VNSI: add channel filter
vdr-plugin-vnsiserver: add channel filter
vdr-plugin-vnsiserver: do not set pts for dts on video streams
vdr-plugin-vnsiserver: raise nice level for vnsi threads
vdr-plugin-vnsiserver: fix a bug in epg auto update
vdr-plugin-vnsiserver: update change log
vdr-plugin-vnsiserver: check and reset modified flag for channels instead of looking at file