Rename Conduit classes

Summary: Ref T5655. Rename Conduit classes and provide a `getAPIMethodName` method to declare the API method.

Test Plan:
```
> echo '{}' | arc --conduit-uri='http://phabricator.joshuaspence.com' call-conduit user.whoami
Waiting for JSON parameters on stdin...
{"error":null,"errorMessage":null,"response":{"phid":"PHID-USER-lioqffnwn6y475mu5ndb","userName":"josh","realName":"Joshua Spence","image":"http:\/\/phabricator.joshuaspence.com\/res\/1404425321T\/phabricator\/3eb28cd9\/rsrc\/image\/avatar.png","uri":"http:\/\/phabricator.joshuaspence.com\/p\/josh\/","roles":["admin","verified","approved","activated"]}}
```

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin, hach-que

Maniphest Tasks: T5655

Differential Revision: https://secure.phabricator.com/D9991