make diseqc tracing comprehensive
tidy up trace spamming
dvb: redo sdt parser to make it more robust

Fixes some problems reported in #hts regarding missing services
eit: forgot to set message as trace
htsmsg: add ability to set/update a u32
tvhlog: created a new logging system that will allow more configuration

Note: I still need to sort out the command line switches
timeshift: fix trace debug.
tvhlog: added hexdump routine.
tvhlog: ignore empty subsys values
tdt: add trace hexdump to sdt/nit parsers.
Merge remote-tracking branch 'origin/pr/268'
dvr: attempt to stop new DVR code creating false entries
tvhlog: fix some silly errors.