Decouple WSFactory from Controller

Issue:

The WSFactory currently has a dependency on starttime and endtime at instantiation, which is behavior expected in the controller.

When used outside the controller, the requirement is not enforced, leading to errors.

• Remove the starttime / endtime from WSFactory constructor to better adhere to the TimeseriesFactory interface.
  • The interface expects starttime and endtime to be provided on call of its methods, not on construction of the class.

Participants:

@erigler @bgeels