BugFix: Prevent colouring of exit number tool-tips on room exit dialog

As referred to in [bug 1369040](https://bugs.launchpad.net/mudlet/+bug/1369040) it has been found that colouration applied to the room numbers displayed in the map room exits dialog to indicate their validity was being passed onto the tool-tips for those elements. The cure is to explicitly apply the colouration to ONLY the QLineEdits involved.

Signed-off-by: Stephen Lyons <slysven@virginmedia.com>