Now all escaping required for the C++ code generation is done when the
.cpp/.h files are generated. Previously, only newlines were escaped
automatically. This was a) inconsistent and b) leaked c++ details into
the xml data.
In addition, the escaping is now done in one central place, harmonizing
the three previous implementations.
Pre-existing c++ escape sequences in the XML files have been replaced by
their literal equivalent so that the resulting python doc sting remains
unchanged.
If package.xml metadata file exists, it is scanned for FreeCAD version
compatibility before the Addon is loaded. If the Addon specifies that it is
explicitly not compatible with the current version of FreeCAD, the Addon is
not loaded.
Rather than trying to use a generic Py::Object and assigning properties
to it, use a Py::Dict object for simple data structures like Url,
Maintainer, and Author.
Update metadata standard to include subdirectory
