Fix confusing button to create folder at root level

The create folder button on the document panel is confusing because the previous version had the action as button in the top panel. This functionality has been moved to popup menu. However user will probably think that has been moved to the button at the bottom.

We need to make it clearer what the purpose of the button is or replace the button with something else. Cheapest solution is to improve the caption of the button that makes clear how it is different from the normal create folder action, and make the button left-aligned.

Proposal caption:
EN: Add root folder
NL: Nieuwe folder op hoogste niveau