Toggle --loop after playback has started via DBus

[superlou]

Is it possible to have OMXPlayer enable and disable the --loop functionality after launch and during playback? I am using OMXPlayer in a live application where the user may decide to stop looping after playback has started.

Looking at how EOF is handled, is this just a matter of setting m_bool, or are there other steps that must be taken to get seamless playback?

[dronus]

Implemented by #679 , adding DBUS command SetLoop, feel free to merge.

[dronus]

Currently #679 implements DBUS command only, but as it is internally by a KeyConfig ACTION it is just missing a code line to assign a key and some update to the README describing this new command.