Identity versioning code reorg

Initial cut at the Identity service refactor in order to implement versioning.
- Split up the Identity class into two separate classes, one each for v2 and v3 of the Identity service. 
- Move all files (requests, specs, etc.) associated with the specific service (ex: Identity v2) into an easily identifiable folder structure by version.

Next PR will handle:
- Finish refactor of Identity code for v1/v2 & specs
- Move requests method out of Identity into requests layer
- Clearly articulate methods of auth (username/pwd, token)