#2035 - Centralize definitions of how thumb/resize filenames are generated.
- added graphics::convert_name_by_size() to convert an item's name/URL/path
for use with a thumb or resize image.
- added graphics::convert_mime_type_by_size() to convert an item's mime type
for use with a thumb or resize image.
- revised item model to use convert_name_by_size.
- revised data_rest to use convert_mime_type_by_size.
- revised file_proxy to use convert_mime_type_by_size.
- changed item::find_by_path to use new function instead of adhoc definitions.
It still requires making some assumptions, which are clearly documented.
For consistency (and without loss of efficiency), we now search for all
thumb/resize images without extensions.
- removed extra unit tests for the png file as it now follows the same case as jpg.