Since QTextEdit::setTabStopDistance() is available starting 5.10 and we
still support Qt 5.5 (Ubuntu 16), it's moved to log_window.cpp and
ifdefed according to version
* 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