Big refactoring.

- Condense api/impl module into single code module, cas-protocol.
- Add configuration module containing common config.
- Refactor webapp module into testbed.
- Refactor action components per changes in dependent IdP modules.
- Only extend AbstractProfileAction where it makes sense.
- Introduce enums for protocol URIs and parameters.
- Refactor ticketing package: TicketStore, TicketFactory -> TicketService.