Migrate Snap saves to a Snap 'Project'

[jhenkens]

Add metadata to Snap 'Project'

• Was the project extended from a base file?
• Is the project a base file itself?
• How many versions does it have/what is the latest version?
• Notes
• Name

[jhenkens]

I messed around with this as a way to have versioning, but have, for now, stashed off the changes and put them elsewhere.

I'll look at it again when we start working more on the versioning system, or potentially the media-extraction system (to store each media object separately in a database accessible by a global id). For the time being, we simply use a snap_file, which doesn't include any native versioning, but does separate the 'project' xml (smaller) from the 'media' xml (larger, contains all the sprite models and sounds).

The project_name, thumbnail, and notes are all extracted from the XML on update and stored in the database as a separate entity for the snap_files#index action.