Adds default-generated UVs to mesh primitives (cone, cylinder, icosphere, uvsphere, cube, circle, grid)
when they are added to the scene, since some of them can be pretty awkward to unwrap manually.
Original patch: Liam Mitchell (CommanderCorianderSalamander).
Main review work: Campbell Barton (campbellbarton).
Finalization, fixes and cleanup: Bastien Montagne (mont29).
Reviewers: mont29, #mesh_modeling, campbellbarton
Reviewed By: mont29, campbellbarton
Subscribers: lkruel, campbellbarton, michaelknubben, kevindietrich
Maniphest Tasks: T37879
Differential Revision: https://developer.blender.org/D481