SemEHR - consider moving plugin to different part of RDMP

[howff]

The SemEHR API has two features which are not used by RDMP at the moment:

• it can return multiple values for each row, i.e. each row returned by a query can contain any of PatientID, SOP, series and study UIDs. The current location of the plugin can only handle a single return column, but if it became a Catalogue it could keep multiple columns
• it can accept a list of values in a query. Currently the plugin only filters the query by Modality and Date range, but the API can also accept a list of PatientID or a list of SOP, series or study UIDs. Using this feature would dramatically speed up the search. This would allow the plugin to become a different part of the conceptual SQL query.

Consider relocating the plugin dialogue to a different part of the RDMP GUI to use these features.