Need to add PATCH API support for Trajectory

We need to make sure that we delete Trajectory elements and stations correctly according to the PATCH API (this is for an element delete).

One thing to pay special attention is: in PATCH API, when you specify any station, the existing stations will be replaced by your station list.
That means
- To replace all stations in trajectory, specify full station list in patch API
- To clean all stations in trajectory, use {“trajectoryStation”:null}
- If you do not want change any station, do not specify any value in “trajectoryStation” property