Version 2.9.0 pre-release

- A new feature allows admins to use the buttons manager to position
directly the XenForo Custom Bb Codes in the XenForo Redactor editor.
This overrides their button default position.
- Redactor buttons coming from the XenForo Custom Bb Codes are now
working with BBM - Thanks to teletubbi
- Buttons Manager code rewritten (a lot php & all the JavaScript)
- Modification done to the code to avoid bugs with other addons - Thanks
to Pegasus
- Modification done to one Bb Code helper - Thanks to Xon
- Improvement of the Buttons Manager Tooltip (disable during sorting
operation)