Improvements to TUX shortcuts

Indicators for insertables were only partially visible,
possibly due to CSS change in core that reduced margin.

* Amend the message to mention the trigger
* Position properly in RTL
* Made the indicators more visible
* Added indicators for up/down arrows
* Removed special case for insertables
* Update indicators after using a shortcut

Change-Id: I16f12ea39ad16a5dfb3d4cf2fd1aeb72bee3343b