Restructure Pyramid includes so that including just any subpackage directly works
Expose Filter, FilterChain, and MissingOriginal classes for import directly from pyramid_frontend.images
Expose save_image, save_to_error_dir(), and check() functions for import directly from pyramid_frontend.images
More adjustments to import locations
Make request.asset_tag() return a literal() so that it doesn't get escaped in templates
Don't register base /_pfe static directory twice
Add settings key to extend Mako template imports, set default filtering to use webhelpers' escape
Add functionality for theme-specific options, which can be overridden in subclasses
Added functionality to map paths to static assets, and override them in subclasses: somewhat mirrors the option API, but without the ability to pass defaults