Media file properties and licensing

[mikaelsvensson]

The ability to upload files using the API is not enough. A license agreement should be attached to all creative works, e.g. photos. Additionally, it should be possible to set a name for each media item.

To do:

• API support for adding licenses to the database.
• API support for editing and deleting licenses. This is only permitted as long as the license is not in use.
• Any license, regardless of whether or not it is in use, can be enabled or disabled. Disabled licenses are not hidden but they cannot be assigned anymore.
• Add attributes to media item: license for item, title of item and name of creator (if not the uploader). License is not required but clients are encouraged to force users to choose one.
• Attributes of license: short name, license summary and full license text. The text is assumed to be Markdown formatted.