Multiple changes:
1) Make action_assets.json compliant with current version of SUIT_ShortcutMgr; Place actions in folders;
2) Make undo/redo meta-actions;
3) Update default shortcut preference file;
3) Fix action names from "Primitives" folder;
4) Change name of shortcut section in preference files;
5) Remove useless entries from test.squish/shared/testdata/SalomeApp.xml.
