* [Web-API/Time Tracking] Implemented 'GET /timetracking/activities.json' in the Web-API for listing available time tracking activities.
* [Web-API/Time Tracking] Implemented 'POST /timetracking/create.json' in the Web-API for creating time tracking entries.
* [Web-API/Time Tracking] Implemented 'PUT /timetracking/123.json' in the Web-API for updating time tracking entries.