dvbsrc: add params for dvr and demuxer
Currently dvbsrc uses the same device number from "frontend" to configure "dvr" and demuxe devices, making it impossible to choose between two different frontends when an adapater has only one dvr and one demux. What I'm proposing here is to fix this issue by adding to more parameters to plugin:
dvr demuxer
With that one has the freedom to use/configure the dvbsrc in all scenarios.