OPAL-1750 NullDatasource used for creating a datasource without storage.
Reverting uppercase of ES operators and fixing error when result is empty
Always specify the sortField when filtering variables
OPAL-1745: New textbox widget with clear icon
OPAL-1745: TextBoxClearable css classes
OPAL-1745: Filter variables filter propagation from variables to values and to entity search dialog
Merge pull request #137 from emorency/master

OPAL-1745: Filter variables with a clear icon and propagation of the filter in between tab selection