Face: Added support for LargePersonGroup operations

[shaibt]

• face:identify() updated to support LargePersonGroups (breaking change)
• face:verify() updated to support LargePersonGroups (non-breaking)
• face: Updated all list() methods to support start/top optional params
• face: updated tests for all additions and changes
• updated api docs with additions and changes

Notes:

• Breaking change in identify() was made to keep it a single API method like the Face API itself.
• Did not add support for LargeFaceLists...maybe someone wants to pitch in?
• only Face API tests were run (all successful). Added test for identify() which was missing beforehand.

[felixrieseberg]

Dang, solid change, thank you very much! This is such excellent work I'll invite you as a contributor to this repository.

[shaibt]

👍