jquery.tablesorter: Support genitive month names

Also use months names from mediawiki.language.months instead of from
wgMonthNames and wgMonthNamesShort. Genitive months names are not
available in that way.

Bug: 46496
Change-Id: If758499fb2d2c2dd02013beaa9cee7b7b8827132
Merge "jquery.tablesorter: Support genitive month names"