- throw exceptions from epub constructor, catch them in metadata gatherer to avoid problems with bad files
- change datetime format in metadata to avoid problems with empty database on some installations
- added metadata extraction for epub documents, these will now have full entries where metadata is available
- metadata is cached in the database
- feed 'entry' template updated to 'full entry' according to OPDS v1.1
- add cover images
- add configurable preview settings (should probably be in core or in a separate app)
- add some metadata to feed template (file size, type and filename)