bluez: update to bluez-5.11
xbmc: make Waveform/Spectrum/FishBMC visualisations optional
busybox: init: check for zero-size *.md5 files

busybox's md5sum applet does not fail if sizeof .md5 file is 0, so
in some rare cases (impropper shutdown before update / broken RPi sdcard)
we may updateto 0byte KERNEL/SYSTEM because md5 check didn't fail

closes #2788
projects/RPi/options: disable FishBMC visualisation
projects/Virtual/options: disable rsxs screensaver and visualisations
linux: sync configs
linux: remove CONFIG_DVB_NET. not used
linux: remove CONFIG_WATCHDOG. not used
linux: remove CONFIG_IP_PIMSM_*. not used
linux: disable CONFIG_RFKILL. not used
busybox: remove applet 'rfkill'