when plotting, update metadata from tiled if run is active

[prjemian]

When fields are selected for plotting and the run is active (which means it is the last run in the database and the run had not stop document, meaning it was still measuring), then update the run's metadata from the tiled server.

Calling the run's .request_from_tiled_server() method will do the update and reset the additional structures to be refreshed from the tiled server.

[prjemian]

Logic for that activity would go here:

gemviz/gemviz/select_fields_tableview.py

Line 46 in b12db35

self.selected.emit(action, self.tableView.model().plotFields())

The code needs the RunMetadata object.