Store data in SQLite (or other database)

[tsukinoinaba]

At the cost of adding a dependency for SQLite, this helps to tidy up the files used by MochiFeed, as it will have only one database file to manage instead of multiple text files. Data will be more organised, as a row in the database can store a channel's tag, RSS feed URL, the latest video seen etc., which reduces the dependency on a channel's position in multiple text files (which could be easily broken by user modification).

[tsukinoinaba]

Will use a single CSV file instead of SQLite, to avoid adding a dependency.