Start: Allow to change the default import module for a filetype

By setting a DefaultImportXXX preferences parameter under Mod/Start,
one can specify a default import module to use when clicking a .XXX
file on the Start page. This is specially useful for filetypes that
have several importers, and the Start page would not let users
choose which importer to use.

Later on if this proves useful we can set up an UI to let the user
set their preferences better.

src/Mod/Start/StartPage/LoadCustom.py

@@ -35,10 +35,9 @@ if cfolders:
     if not os.path.isdir(cfolder):
         cfolder = os.path.dirname(cfolder)
     f = unquote(filename).replace("+", " ")
-    if f.lower().endswith(".fcstd"):
-        FreeCAD.open(os.path.join(cfolder, f))
-    else:
-        FreeCAD.loadFile(os.path.join(cfolder, f))
+    ext = os.path.splitext(filename)[1].lower().strip(".")
+    mod = FreeCAD.ParamGet("User parameter:BaseApp/Preferences/Mod/Start").GetString("DefaultImport"+ext,"")
+    FreeCAD.loadFile(os.path.join(cfolder, f),mod)
     FreeCADGui.activeDocument().sendMsgToViews("ViewFit")
 
     from StartPage import StartPage

src/Mod/Start/StartPage/LoadMRU.py

@@ -19,10 +19,16 @@
 #*                                                                         *
 #***************************************************************************
 
+import os
+import FreeCAD
 import FreeCADGui
+
 # MRU will be given before this script is run
-rf=FreeCAD.ParamGet("User parameter:BaseApp/Preferences/RecentFiles")
-FreeCADGui.loadFile(rf.GetString("MRU"+str(MRU)))
+rf = FreeCAD.ParamGet("User parameter:BaseApp/Preferences/RecentFiles")
+filename = rf.GetString("MRU"+str(MRU))
+ext = os.path.splitext(filename)[1].lower().strip(".")
+mod = FreeCAD.ParamGet("User parameter:BaseApp/Preferences/Mod/Start").GetString("DefaultImport"+ext, "")
+FreeCADGui.loadFile(filename, mod)
 
 from StartPage import StartPage
 StartPage.postStart()