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