Refactor DB

Revamp the database layer. Separate DBHelper into two classes; SQLiteDAO
and SQLiteDBHelper. The DAO will act as the interface to the database
for other classes and be responsible for maintaining the database
connection, inserting, deleting, etc. The DBHelper will be responsible
for CRUD operations; creating the database, dropping tables, updating,
reading. Hopefully this will simplify things a bit.

Move loose text in xml files to the strings.xml.

Rename xml files for more consistency.

Remove extra buttons from ingredients fragment. Prepare for using the
action bar.