Home page - ordering apps

Related to #18, specifically the line:

> * Allows to modify the apps order

Under **Home page**.

This should be extended to something more specific. Namely, the ordering should be done in a more agile and easy way, instead of now, where one has to click several times to set the order of apps.

Change suggestions:
- Create pop-up window, where the order may be set.
- Have a separate notebook (with app-mode), where the order may be set.
- Drag-and-drop the existing apps directly on the home page to reorder.
- Give each app a number to the side that may be changed directly on the home page.