Django-clubhouse

- Added django-image-cropping as a requirement to installation for new widgets
- Added easy-thumbnails as an installation requirement for new widgets
- Ensuring BlockContext.get_block_models doesn't yield the same model twice

- Updated render_blocks tag context variable from 'block_context' to 'context_model', more explicit
- Implemented core.options.serializer_registry for registering serializers against models and looking up serializers for models
- Implemented core.options.autodiscover_serializers for discovering serializer module
- Added utils.models.ensure_model function to take either model class, or "app_label.ModelName" string and return model class

- Using a 'block_models' property on BlockContext in addition to Block.block_contexts when collecting blocks for BlockContext
- Added .order_by to render_blocks template tag block query
- block_render tag now accepts any kwarg, which it then uses as base context.
- block_contexts Block property can now use "app_name.ModelName" syntax, as can BlockContext.block_models

- Deprecated core.serializers.BlockSerializer
- Added find_for_model function in core.serializers
- core.serializers.BlockContextSerializer uses find_for_model for block_object

- Support for image_cropping crop fields with Filebrowser
- Added clubhouse.core.fields.FileBrowseImageField
- Added clubhouse.core.widgets.FileBrowseImageWidget
- Added clubhouse.core.widgets.FileBrowseImageCropWidget
- Added clubhouse.core.options.FileBrowseImageCroppingMixin
- Added utils.image with ImageCroppingHelper
- Added have_fields_changed to model utility
- Overidden template filebrowser/custom_field.html

- Migration added