DM-6908 Add filter editor to the chart toolbar

[tgoldina]

• Added filter editor to the charts toolbar
• When filtering returns empty data set, server side will return header. Before, it was returning \Loading-Status = COMPLETED, and TablesCntlr:265 would never activate a new table callback.
• Charts are cleared when table data are being fetched.
• Label and unit in XYPlotOptions will now get cleared whenever x or y changes
• removed tbl_id from CatalogWatcher and CoverageWatcher's server requests to prevent interference with the table
• changed the order of lat,lon->lon,lat in CoverageWatcher's server request (just for consistency: it was dec, ra before)

[loitly]

clear filter button disappears after a region is selected.

• apply a filter, clear filter button appears on top-left.
• select a region in xyplot, clear button disappears.

[loitly]

clear filter text did not clear filter.

• apply a filter. ie. ra > 0
• select the text 'ra >0' then press 'delete'. tab or enter to apply the change. nothing happen.

[loitly]

table in filter editor is not sortable.

• click on 'Column' column, nothing happen.

[loitly]

Done with review. Code is good. There are several things I pointed out above that may need fixing.

[loitly]

It looks good. Good to merge.