Restore 'Close Tab' on the tab context menu and the close tabbar button.

These 2 options were disabled due to they messed up the menu texts
after the fix for bko 185466.
The close method via dbus has been disabled as it causes menu issues.

Most of patch to fix 'Close Tab' by Albert Astals Cid aacid@kde.org
CCBUG: 267896
CCBUG: 185466
FIXED-IN: 4.6.3
CCMAIL: aacid@kde.org
(cherry picked from commit 467fb1ed)