Move LibraryLoader to a builder pattern.

I made the old static methods deprecated and removed the new generateMipMaps parameter from them.
Presumably if anybody other than me is already using it, they're paying enough attention to adapt
to this change too.
Enable external frankenweenies.

There are two approaches in use here:
 * Several points in loading dispatch a signal:
 ** file loaded from the .zip that wasn't recognized
 ** the library mold was loaded
 ** a ATF atlas was loaded
 ** a PNG atlas was loaded

I didn't end up needing all of these: I have no immediate use for the library mold signal, but it
seems generally useful, and I don't know what someone would even do with the ATF data other than
create a texture with it, but it seemed sensible to include it for completion.

 * a SymbolCreator factory pattern for letting flump consumers create custom MovieCreators and
   ImageCreators, giving them complete control over the final class that ends up on screen.

With the combination of these two, I have alpha based hitTesting for Images in my project, with
minimal memory impact.

Example gist for alpha hit testing: https://gist.github.com/roguenet/5651658