Implemented model for bills.
Implement UserBillShare object
Merge branch 'dev' into feature-bill
Prepare BillController
- Write repository method to find bills of an account.
- Add a bill overview page.
Add Bill form and create action
Add method to abstract form to get action collection (for modifying title ect.)
- Implement rest of UserBillShare model
- Add add-purchase view
Fix annoying bug concerning doctrine one to many unidirectional relationship.
Add call to parent constructer to fix exception.
Implement deletion of bills (inlcuding UI)
Fix bug in entity share.

the inverse side of the bill property was not set, and thus not saved to the DB.
Implement users view for bill
Implement add user to bill.
Add user button to bill list.
Change name of add user button
Add view action to Bill controller
Enchance bill object.
Add script to generate ctags (for vim autocompletion).
Add getAmount method to bill.