Draft: Disabled automatic DXF library download - fixes #1785

Note for existing users: Can be reenabled in menu Edit > Preferences >
Import-Export > DXF > Automatic update
+ port Sandbox module to Quarter
+ harmonize API
+ harmonize API
+ support of home path with non-ASCII chars
+ fix more Quarter port issues
+ fix Python binding of 3d viewer
+ save last used export/import filter
Output Mac OS version (or Windows 8) on splashscreen
+ formatting message
+ remove useless statement
+ make help system more flexible
Merge branch 'master' of ssh://git.code.sf.net/p/free-cad/code
+ fix problem with disappearing content of image view
+ fixes #0001794: new defined as a macro sometimes conflicts with boost
+ change API of GLPainter
+ port cache context handling
+ fix bug in Python binding of Quarter viewer
Added commands Sketch_BreakLine and Sketch_SplitLine.
Added new commands to PartDesign and Sketcher.
Added initial icons for Sketch_BreakLine and Sketch_SplitLine