Refactor and rename rest of libKGoogle core

- KGoogleAccessManager is now KGoogle::AccessManager
- KGoogleObject is now KGoogle::Object (and objects are in KGoogle::Objects namespace)
- KGoogleService is now KGoogle::Service (and objects are in KGoogle::Services namespace)
- KGoogleRequest is now KGoogle::Request
- KGoogleReply is now KGoogle::Reply

All classes were ported to the new authentication framework, KGoogle::Request now holds
KGoogle::Account which AccessManager then uses to obtain authentication and/or automatically
refresh it's tokens if neccessary.