Search rc1 fixes develop

This is #2855 rebased onto develop.

--rebased from #2855.

Fixes a couple of issues noticed during RC1 testing.

To test:
 - Search by multiple IDs separated by whitespace or commas. All matching images should be shown.
 - Selecting images in a 'share' tree should update the selection in the center thumbnails. Only a single image selected at a time.
 - On search page, open date-picker for 'To' date and double-click on a future date (nothing selected). Then close date-picker and open the 'From' date-picker. Check that the 'max date' is still restricted to current date.