[CTFGUILD-10] Modified CTFUser class according to the task
Added OCMock to the workspace.
Wrong code removed.
Added CTFUserService class and tests for it.
CTFCredentialsValidator class refactored and renamed to CTFAPICredentials
Added additional case to CTFAPICredentialsTests.
Added CTFAPIConnection and CTFAPISignIn classes.
Renamed CTFAPISignIn to CTFAPIAccounts.
AFHTTPClient replaced by RKObjectManager.
Added tests for CTFAPIConnection.
Added tests for CTFAPIAccounts.
Added CTFLocalCredentialsStore, CTFLocalCredentials, STKeychain for managing credentials in Keychain.
Added tests for CTFlocalCredentials.
Added tests for CTFLocalCredentialsStore.
STKeychain fixed after refactoring.
Implemented ability to remember credentials typed in sign in process.
Fixed AFNetworking warnings.
Added tests for currentUser method of CTFUserTests.