Tvheadend

Please add dynamic device handling for tvheadend.

Tvheadend should be able to handle added/removed devices at runtime.
When the dvb device is removed from usb (power off) and tvheadend tries to access it, tvheadend is crashing.
When no device is available maybe some static image could be streamed with a message "no device free/available at the moment".

Reason for this request: My dvb-s2 tuner needs about 6W when in "power safe state". I dont want to restart tvheadend on the server everytime i power off/on the dvb-s2 device.