R1:023dee0d3b6d

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.