Bugfix: Show loading indicator when refreshing.

The loading indicator is shown when fetching data.
Feature: Filter widget support added

* The meta-analysis for genes now show the filter widget and allow filtering of the lists.
* Instead of a ListDataProvider a AsyncDataProvider is used (which fixes the display and
 the pager)
 * If no gene is loaded, then the DataGrid will show the loading indicator
Feature: Upload functionality added to candidate gene list

Users can now upload csv containing one column with gene ids. They will be added to the
 candidate gene list.