Mesh modeller april update

[xbx]

Detailed changelog for the meshmodeller:

• - Import Mesh : Creates custom Mats if needed
  - Import Shape : Creates custom Mats if needed
  - Import Shape : Creates Triggershape Layer if needed (or add it to Triggershape layer already existing)
  - Materials : can't be used outside of envis
  - 3 UV Layers Materials (Turbos) : banned until good solution made
  - Camera handling : more precise, alt clic works as intended, doesn't interrupt what you were doing, better helpers display
  - Parts Merging : fixed issues
  - Copy Paste (and BlocTransfo and Mirror) : fixed crash with Parts being wrong
  - Shadow calc : cancelled if you saved and exit without any modification
  - Smooth Crystal : back in the game and has a better tolerance
  - Exit : Fixed a crash that was happening when editing a layer
  - Delete Mesh from item editor : was causing a crash after reloading the game cos it was at null
  - Layers tied together : Fixed
  - Step : can now be modified freely by typing the number you want
  - Fixed a memleak when loading materials of an item
  - Voxels / Cubes : fixed a lot of crashes linked to automatic Parts
  - Fixed red materials even though everything was expected to work
  - Fixed crashes when creating a BlockItem
  - New UI
  - Fixed Picking Materials in Titlepacks
  - Fixed Import Mesh from Titlepacks
  - Fixed Custom Materials management in Material Lib
  - Fixed Selection management, especially during AutoSave