Added the fmdb library
Moved all the libraries into the right place and removed the (unused) JSONKit library
Extracted some of the functionality from the CatapultAccountsTableViewController to the newly created CatapultAccount model. Also moved the constants in the header files.
Moved the import statements to the header files.
Multiple changes:

- Created a BaseModel that takes care of the database connections.
- Added some methods to the AccountModel
- A user can now delete an account
- When a user tries to add an account, the app first checks if that account was already added.
Implemented the signOut method (finally) + a couple other tweaks