[FIX] tablesorter: text in input fields wasn't showing

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@53302 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] tablesorter: make the column selector popup appear upon hover like the other buttons; add some documentation

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@53303 b456876b-0849-0410-b77d-98878d47e9d5