merging in new wearable infrastructure to get a step closer to eventually...

merging in new wearable infrastructure to get a step closer to eventually supporting multiple wearables per type. Merge tested and compiles/working on linux and windows - no obvious regressions on appearance or appearance editor. Merge generated no conflicts due to being tested in fresh re-branch in avatar-pipeline/multiple-textures-12. Merge perfomed with following command:

svn merge -r 136489:136510 svn+ssh://svn.lindenlab.com/svn/linden/branches/avatar-pipeline/multiple-textures-12 .

Progress can be tracked in DEV-32551.

 -Nyx