change the way of handling live streaming

Do not stop the streaming client if the receiver gets detached.
The live-streamer constantly tries to attach to any available receiver
to serve the streaming request. VDR notifies about stream changes via
the newly introduced ChannelChange() status message.
proper server shutdown
do not write channelcache twice
send status messages if switching channels fails
i18n: added german translation
i18n: translation fixes

- fixed empty language fields
- removed autogenerated xvdr.pot from git
- updated .gitignore
livequeue: fixed invalid access
concurrent access locking in cLiveStreamer::IsReady()