removed ambiguous parameter "set_by_user" from many places in codebase,
renaming it to be upload_bake, which is a more accurate descriptor.
This allowed me to see several inconsistencies in how this variable was
being set - these errors were also fixed. User-visible result should be
that baked textures are not reuploaded on changing avatar sex until the
save button is pressed. primary win here is code clarity.

Code reviewed by Bigpapi.