New feature: Edit Sketch datum constraints from data Property view

This feature shows in the data properties associated to a TreeView element,
the datum constraints, i.e. those with an associated value.
+ fix build failure on Windows, remove unused headers, whitespace improvements
Fix bug 1643: Projections are always added to the first drawing page
Fix typo.
1659: 3dconnexion space navigator moves view even when FreeCAD is not the active application

Check whether the freecad window is active before relaying the space navigator events.
+ suppress annoying warnings with MSVC for SMESH sources
+ fix trim mesh with plane
Sketcher properties feature enhancement: Separated sublist for unnamed datum constraints
Draft: removed unnecessary latin1 decode operations
+ fix DrawingView::onRelabel() to accept any page names
+ port RegExp utility to Qt4
Merge branch 'master' of ssh://git.code.sf.net/p/free-cad/code