Deleting a contract causes deletion of all contracts of said creator

[Eitan-Lev]

When withdrawing both parties' funds, the factory.removeDeposit() is called, then delete deployedDeposits[(depositsCreators[msg.sender])] is done.
This deletes all the contracts belonging to sender, instead of just the specific one.
Tricky to fix- we work with an array, and don't want to leave an empty cell in the middle.

[Eitan-Lev]

The index number is returned when performing push, so we can use it to save and later refer to it. Makes it relatively cheap.