refactor: split most of Factory out to FactoryLib

[BenSparksCode]

Changes:

• In order to cut down Atlas contract size, we've started the contract splitting with Factory.
• Atlas is used as the endpoint contract for a lot of the external Factory functions in tests and testnet deployments, so these have been left in Factory, as well as the internal functions called inside Atlas. The salt calculation function has also be left in Atlas.
• The rest of the factory logic as been moved to FactoryLib, a new contract which is delegatecalled by Factory. FactoryLib must be explicitly deployed separately and configured as a constructor param in Atlas.
• This results in a 524 bytes decrease in contract size.