new-style-modules: adding the possebility to import from "freecad"

(this mostly aims at new modules and extension modules which want to use pip)
- any module having problems with nameclashes can use this syntax (from freecad import module)
- current imports still work (backward cobatibility)
- python extension moduels can be installed (pip) to python std path (eg.: site-packages)

- adding app, gui to the new freecad package:
```
from freecad import app
from freecad import gui
```

- syntax for importing c++ extension will not change
```
import FreeCAD as App
import FreeCADGui as Gui
```

src/App/FreeCADInit.py

@@ -58,6 +58,8 @@ def InitApplications():
 	# Checking on FreeCAD module path ++++++++++++++++++++++++++++++++++++++++++
 	ModDir = FreeCAD.getHomePath()+'Mod'
 	ModDir = os.path.realpath(ModDir)
+	ExtDir = FreeCAD.getHomePath()+'Ext'
+	ExtDir = os.path.realpath(ExtDir)
 	BinDir = FreeCAD.getHomePath()+'bin'
 	BinDir = os.path.realpath(BinDir)
 	LibDir = FreeCAD.getHomePath()+'lib'
@@ -75,6 +77,9 @@ def InitApplications():
 	#print FreeCAD.getHomePath()
 	if os.path.isdir(FreeCAD.getHomePath()+'src\\Tools'):
 		sys.path.append(FreeCAD.getHomePath()+'src\\Tools')
+
+
+
 	# Searching for module dirs +++++++++++++++++++++++++++++++++++++++++++++++++++
 	# Use dict to handle duplicated module names
 	ModDict = {}
@@ -116,7 +121,7 @@ def InitApplications():
 	# also add these directories to the sys.path to 
 	# not change the old behaviour. once we have moved to 
 	# proper python modules this can eventuelly be removed.
-	sys.path = [ModDir, Lib64Dir, LibDir] + sys.path
+	sys.path = [ModDir, Lib64Dir, LibDir, ExtDir] + sys.path
 
 	for Dir in ModDict.values():
 		if ((Dir != '') & (Dir != 'CVS') & (Dir != '__init__.py')):
@@ -141,6 +146,24 @@ def InitApplications():
 			else:
 				Log('Init:      Initializing ' + Dir + '(Init.py not found)... ignore\n')
 
+	extension_modules = []
+	import pkgutil
+	import importlib
+	import freecad
+	for _, freecad_module_name, freecad_module_ispkg in pkgutil.iter_modules(freecad.__path__, "freecad."):
+		if freecad_module_ispkg:
+			Log('Init: Initializing ' + freecad_module_name + '\n')
+			freecad_module = importlib.import_module(freecad_module_name)
+			extension_modules += [freecad_module_name]
+			if any (module_name == 'init' for _, module_name, ispkg in pkgutil.iter_modules(freecad_module.__path__)):
+				try:
+					importlib.import_module(freecad_module_name + '.init')
+					Log('Init: Initializing ' + freecad_module_name + '... done\n')
+				except ImportError as error:
+					Err('During initialization the error ' + str(error) + ' occurred in ' + freecad_module_name + '\n')
+			else:
+				Log('Init: No init module found in ' + freecad_module_name + ', skipping\n')
+
 	Log("Using "+ModDir+" as module path!\n")
 	# new paths must be prepended to avoid to load a wrong version of a library
 	try:

src/CMakeLists.txt

@@ -5,6 +5,7 @@ add_subdirectory(Base)
 add_subdirectory(App)
 add_subdirectory(Main)
 add_subdirectory(Mod)
+add_subdirectory(Ext)
 if(BUILD_GUI)
 	add_subdirectory(Gui)
 	configure_file(Doc/freecad.qhc ${CMAKE_BINARY_DIR}/doc/freecad.qhc COPYONLY)

src/Ext/CMakeLists.txt

@@ -0,0 +1,6 @@
+# this directory is the entry point for extension modules. Any package
+# installed to a directory "freecad" which is in sys.path can be imported
+# with "from freecad import package" and is checked for a init_gui.py 
+# module, which is import at startup. (FreeCADGuiInit.py)
+
+add_subdirectory(freecad)

src/Ext/freecad/CMakeLists.txt

@@ -0,0 +1,20 @@
+EXECUTE_PROCESS(COMMAND ${PYTHON_EXECUTABLE} -c 
+"from distutils.sysconfig import get_python_lib; print(get_python_lib())"
+OUTPUT_VARIABLE python_libs OUTPUT_STRIP_TRAILING_WHITESPACE )
+SET(PYTHON_MAIN_DIR ${python_libs})
+
+SET(EXT_SRCS
+    __init__.py
+)
+
+ADD_CUSTOM_TARGET(freecad_COPY_SOURCE ALL
+    SOURCES ${EXT_SRCS})
+
+fc_copy_sources(freecad_COPY_SOURCE "${CMAKE_BINARY_DIR}/Ext/freecad" ${EXT_SRCS})
+
+INSTALL(
+    FILES
+        __init__.py
+    DESTINATION
+        Ext/freecad
+)

src/Ext/freecad/__init__.py

@@ -0,0 +1,4 @@
+import pkgutil
+__path__ = pkgutil.extend_path(__path__, __name__)
+
+import FreeCAD as app

src/Gui/FreeCADGuiInit.py

@@ -131,8 +131,27 @@ def InitApplications():
 				Log('Init:      Initializing ' + Dir + '(InitGui.py not found)... ignore\n')
 
 
+	import pkgutil
+	import importlib
+	import freecad
+	freecad.gui = FreeCADGui
+	for _, freecad_module_name, freecad_module_ispkg in pkgutil.iter_modules(freecad.__path__, "freecad."):
+		if freecad_module_ispkg:
+			Log('Init: Initializing ' + freecad_module_name + '\n')
+			freecad_module = importlib.import_module(freecad_module_name)
+			if any (module_name == 'init_gui' for _, module_name, ispkg in pkgutil.iter_modules(freecad_module.__path__)):
+				try:
+					importlib.import_module(freecad_module_name + '.init_gui')
+					Log('Init: Initializing ' + freecad_module_name + '... done\n')
+				except ImportError as error:
+					Err('During initialization the error ' + str(error) + ' occurred in ' + freecad_module_name + '\n')
+			else:
+				Log('Init: No init_gui module found in ' + freecad_module_name + ', skipping\n')
+
 Log ('Init: Running FreeCADGuiInit.py start script...\n')
 
+
+
 # init the gui
 
 # signal that the gui is up