[reports] Table/Figure adding pop-up does not have a dismiss button

This one keeps coming in and out and we must fix it because it is really counterintuitive in the way it is implemented today.

Little cut-n-paste from our dev mailing list:

JG: ISSUE 2:
You create an experiment.
You create a report.
You add the experiment to the report.
You add a table --> results.
You select the results that you want to include in the table by ticking the boxes on the left.
Once you have finished selecting the results... what do you do?

I think it would be nice to have a "DONE" button at the bottom of the window where you select the results to be displayed in the table. This way when you finish selecting the results, you press the "DONE" button and it takes you back to the report.