+ share GL widgets when creating further 3d views of a document
+ fix build failure
issue #1788 SVG output of trimmed curves
fixes #1706 rename anaglyph stereo mode red/cyan
move exportDRAWEXE.py to Sandbox WB
+ fixes #0001779: memory leak
+ fixes #0001735: Ellipsoids visibility problems
Draft: Disabled automatic DXF library download - fixes #1785

Note for existing users: Can be reenabled in menu Edit > Preferences >
Import-Export > DXF > Automatic update
Merge remote-tracking branch 'upstream/master'