Filled in methods for DatabaseModel class

author: Amy Zhang

Used SQLite's query, update, insert, and delete methods for our database
model class. Someone should probably look over these to make sure I did
them right.

The query commands return a Cursor object. I haven't figured out how to
parse that yet, but I put TODOs to mark the task.

This will definitely need some serious testing, but as of right now it
compiles alright.
Merge branch 'master' of github.com:jfmyers9/ThePantry

Git pulling to update and push