Merge changes from develop branch

Top level navigations using Tabs.
Dashboard displays all virtual devices as live tiles (panoramic scaling is disabled for now).
Tiles are coloured based on the current power consumption or temperature.

Still pending:
Disable refresh of device list when not in focus.
Generalize the tile generation function by accepting a parameter so that same function can be used for tile display in other tabs as well.
General code cleanup and optimisation.