created a leveled validation message interface and a default implementation with some factory methods for creating instances
added 'propertyName' to ValidationMessage and the factory methods.  made the default implementation's fields final.
set up a validation framework, and validated cardsets.  card validation is present, but a no-op at this point.
implemented the validation command's functionality
changed FontLoader to operate on URLs instead of classpath paths, though the latter is still available via backwards-compatible helpers
moved font registration out of the theme code and into the theme descriptor
put the font and texture stuff into a 'library' wrapper to better differentiate it from the direct-access descriptor elements
added loading font attributes from the descriptor to replace the hard-coded stuff
removed unneeded @SuppressWarnings
moved the font specification information out of DefaultLayout and into the descriptor
brenna says i am bad at text, but magic numbers fix EVERYTHING!
changed Texture to use Rectangle2D instead of just Rectangle
did a bunch of refactoring to put the target regions in the theme descriptor, instead of in the code
renamed 'areas' to 'regions' throughout