Update Overview to include more relevant sensors

This adds a few small features and updates the Overview page to include a bunch more relevant sensors:

• The first row now contains CPU, GPU, Memory and Swap usage.
• The second row Disks, Batteries and Networks.
• The last row consists of the applications table, but using a new height mode where it's allowed to take half the page height. In addition, it now contains a toolbar showing the table's actions, similar to what's shown in the page toolbar for the applications page.

Screenshot:

This depends on !352 (merged)