Restructure the Toolbar

This patch restructures the toolbar, in order to adhere to the KDE's HIG:
https://techbase.kde.org/Projects/Usability/HIG/Toolbar

- Actions not-so-frequently used are removed
- Most used actions (like Extract) are now the first ones in the toolbar
- A separator is introduced

Differential Revision: D1180

(cherry picked from commit 7777f964 on master, as Applications/16.04 was branched without it)