installation: Flask-OAuthlib upgrade to 0.6

* Changes the setup file so flask-oauthlib will be the latest version,
  that is 0.6.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
oauth2server: oauth2server improvements

* Removes the oauth parameter from some functions.

* Adds '/' to the endpoints that need it in the test_provider.

* Changes some 403 to 401 in the test_provider.

* Uses the url_for in some functions in helpers testsuite in order to
  hard-code the url.

* Tests the test_provider case.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
documents: documents REST API changes

* Removes `oauth` parameter from REST API functions.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
deposit: deposit REST API changes

* Removes `oauth` parameter from REST API functions.

* Adds `base_url` to a `test_registration`.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
tags: API and REST API fixes

* Removes `oauth` parameter from REST API methods.

* Ensures tests are passing.

* Adds an `uid` parameter to the method that attaches tags to records.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
restful: decorator improvement

* Improves require_api_auth decorator by clearing the session
  and returning the response at the end.

* Removes the bound_instance_ parameter, removes the
  require.oauth from the return statement and the returned
  function now contains only the *args and the **kwargs.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>
oauth2server: compatibility improvements

* Removes the `oauth` parameter from some functions.

* Adds '/' to the endpoints that need it in the test_provider.

* Changes some 403 to 401 in the test_provider.

* Uses the `url_for` in some functions in helpers testsuite in order
  not to hard-code the url.

* Tests the test_provider case.

Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>