(ui): add sequencer limitations

Description

Add an option to remove all the data generated when going backward with the sequencer.

• display a dialog to inform the user that the data will be removed and ask to continue.
• remove all the following activities and their data.
• disable the following activities.

Also fix a few layout problems, the buttons required a width to be properly displayed.

Closes #782 (closed)

How to test it?

Add the tag true in your sequencer configuration (for example, in ExActivities). Test to go forward and backward. Check that the sequencer still work as before without the option.