Removed Database class because the internal abstraction of SQLiteHelper
was causing concurrency issues that could not be solved in the class.

Migrating convenience methods to Model class that all take an
SQLiteDatabase object as an argument.
Migrated lost convenience methods from Database class to Model. Updated
example classes to reflect changes.
Regenerated javadoc.
A bunch of changes. (I forgot them all.) Also regenerated javadoc.
Commit