CORE-4876 Fix for file size search queries.

Updated DiskResourceQueryForm to convert numbers in the file size text boxes into bytes, according to the units selected in the file size combo-boxes.
Added a "bytes" unit to the file size combo-boxes, for ease of conversion as well as allowing finer grained search values for the user.
CORE-4876 Fix for date range default selection.

Updated the created and modified combo-boxes in DiskResourceQueryForm to use the same empty text as their "null" selection labels, since their values set at initialization will be overridden by values set in the edited model.
CORE-4876 Refactor file size LabelProvider.

Moved the LabelProvider for the DiskResourceQueryForm file size combo-boxes into their init method.
CORE-4876 Updated search grid header text.

Added execution time in seconds.
Removed implicit asterisks from the search text in DiskResourceSearchField, since the DataSearchQueryBuilder automatically adds them, which allows only the text the user typed to display in the results header text.
Added quotes around searchText param, only if a file name query was provided by the user, otherwise a generic search phrase is displayed.