Revert "The Cache can now be generated as a const object."

This reverts commit 8df46d0d2a66e2d886eeeab39eaa7a26c8de6b73.
It didn't make no sense. The problem of finding the cache with a const
object can be solved in other ways (for most cases, any cases I need
here.)
No need for a copy from the get_dependency function. It now returns a const reference.
Fixed the Menu Animation.
Added a grab_dependency function to the Cache.

See the documentation for the documentation!
The Label now uses the new-fangled Texture_Cache.