[ENH] tablesorter: Apply group header rows. Other minor cleanup.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@53209 b456876b-0849-0410-b77d-98878d47e9d5
tablesorter: use btn-link for less obtrusive table buttons and pager controls

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@53210 b456876b-0849-0410-b77d-98878d47e9d5