IDevice: Update icons indicating device state.

Simple dots in
 - red (device disconnected)
 - yellow (device connected but not ready to use) and
 - green (device connected and ready to use).

Change-Id: I04155a917e23351bb9d1125a432957ef05b64ef5
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>
Reviewed-by: Christian Kandeler <christian.kandeler@nokia.com>