Texture Importer Refactor - Use the cache better

I don't know what this texture importer refactor is, but I'm jumping on board with my own requests!

I want to move our project to mostly crunched dxts, cause they are awesome and small, however I don't want to subject the team to the crippling import times.

We have the cache server, but it regularly fails on initial import and project update (Case 759902)

Secondly, some genius caused all the textures to be reimported for every platform, is a Win 32 dxt different from a Win 64 dxt, different from a OSX dxt? Nope. I couldn't stand the 5x reimport of crunched textures for each platform we ship (Win32,OSX universal, linux universal, PS4, XBoxOne).