Camera Sets support and PointCloud-based selection

[yann-lty]

• New Features:
  • Camera Sets: create camera sets within MayaMVG
  • Particle Selection: filter cameras based on points visibility
  • Filter Points: display points based on a minimal visibility score
  • Swap the 2 MayaMVG views
  • Set persp's pose from a MayaMVG camera
• Bugfixes:
  • Lock MayaMVG camera nodes to avoid unwanted deletions
  • Crashfixes on undo/redo