Support multiple video resolutions

[Alanaktion]

Once #17 is complete, it should be improved to record the resolution of each local file in the database, and allow the user to select a resolution/file in the player/download.

• Add resolution to video_files table. Maybe just a single height value or multiple width/height ints?
• Add command to add resolution information to database for existing files
• Update import:filesystem to add resolution information to database on import
• Allow selecting resolution/source when multiple resolutions are available

[Alanaktion]

Maybe also record the codecs found on the file for use in the HTML5 codecs parameter on the player sources, etc.