OC_OCS_Result Class, Only accept 100 code as success

See spec: http://freedesktop.org/wiki/Specifications/open-collaboration-services/

Only 100 codes seem to be an actual successful response.

Mentioning those I know using the api code / involved: @karlitschek @ser72 @DeepDiver1975 @schiesbn @PVince81 

I think this should be the first step in moving to HTTP codes, both in the OCS methods and other apps. This would solve quite a few issues including https://github.com/owncloud/core/issues/7858

I would like to push for HTTP response codes in ownCloud 7. 

This lets us send a proper HTTP header instead (or in addition to) sending it in the body.

TODO:

- [x] Adjust unit tests https://github.com/owncloud/core/blob/master/tests/lib/api.php