Changed position and label of 'Changed(Hrs)' filter

This setting is actually not a filter but a display option that
just highlights the last updated date. The field has been moved next to
'Sort by', and its label changed to reflect its real function.

Fixes 0007737

This is a port of the original 1.2.x commits from the pull request
(squashed).

Signed-off-by: Damien Regad dregad@mantisbt.org