Extend taggable-mixin to support different Tag models.
Usage is pretty simple. Tag model is default in Taggable constructor but you
can call it with different model like GHOPTaskType that inherits from Tag model.
Both Taggable and Tag models have been updated and they don't use hardcoded Tag
model anymore and instead use cls of class methods or self.__class__. In case
of Taggable it's self.__tag_model.
Third-party code that is *not* part of the application image (the Google App
Engine SDK in trunk/thirdparty/google_appengine, for example) belongs in
trunk/thirdparty. For third-party code that *is* part of the application
image, see the notes in trunk/app/README.
== THIRD PARTY LICENSES ==
Third-party code must also include a license text file, named LICENSE or
COPYING, in the package subdirectory. If the third-party package subdirectory
is maintained automatically with a tool such as svn_load_dirs.pl (which
removes files, such as license text files, that were added later to the
"target" directory), place the license text file in the trunk/app directory
and add the package name as a suffix.