Add full jones solve

This MR adds a direction-independent full-Jones solve as part of adding support for QUV imaging to Rapthor (see RAP-423). A new strategy parameter (do_fulljones_solve) was added to control when the full-Jones solve is to be done (by default it is disabled). This MR does not enable the generation of QUV images, as this will be done in RAP-422. Further testing and tuning of the QUV solve will be done as part of RAP-466.