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 #7737

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

Signed-off-by: Damien Regad <dregad@mantisbt.org>
Move 'Highlight changed' field in view_filters_page.php
Changed(hrs) "filter" is now labeled 'Highlight changed'

Pull request #81