This lowers the chance of getting an already used port. This is still
not perfect as the port could still be taken before ug starts, but
should be good enough until we invert the client-server relationship
between gui and ug for control-port.
Blocking until the process is finished was not very robust - in some
cases it could cause a deadlock preventing graceful exit. For example,
if the ug process is communicating with GUI through a socket and uses
blocking send - ug will wait for GUI to receive the data and GUI will
block waiting for ug to terminate.
Using this approach also allows to ignore crashes on exit, which are not
really worth reporting.
* use ug --capabilities for querying
* support for webcams on Windows and MacOS
* support for decklink capturers and modes
* query v4l2 through UltraGrid
* don't store state in ui widgets (preparation for saving/loading settings)
* automatic FEC
