First-pass at Qt Client API for Phoenix web services.
The underlying project data is organized as the basic 'p4_project_services' API, which is then used by the higher-level 'phoenix' API, just to cut down on a lot of potential boiler plate. The base project model should allow for custom extensions, but it's aniticpated that the product-specific stuff doesn't really need to care too much about this. We just need to make sure that if new product extensions exist that the C++ API doesn't know about, they: a.) don't explode on read because there's something new, and b.) don't just delete the extension code.
These are *just headers* to get the ball rolling on the needs of the Phoenix engine. Things like 'sessions' are interesting and may have been overlooked.