make read() fail with TwistedConnector
VRTClient with callback for packets arriving
vrt_callback: pass through from TwistedConnector -> VRTClientFactory -> VRTClient
update gui for TwistedConnector changes
remove twisted_util (no longer used)
update twisted_show_i_q example
Merge pull request #15 from wardi/vrt-callback

TwistedConnector: use simpler, more general callback approach for when VRT data arrivals
remove outdated twisted test
WSA4000: stream_start, stream_stop, stream_status
:sweep:flush no longer exists
WSA4000: add system_flush, system_abort
Revert ":sweep:flush no longer exists"

This reverts commit 9657756f253b71286085b664df06928bf496e6f3.
:sweep:flush is dead; long live :system:flush
rename system_abort to abort, more like other methods
WSA4000: improve spp()
stream speed test example
wsa4000gui: start using streaming mode
wsa4000gui: keep all vrt context values received
wsa4000gui: stop and start stream capture around setting changes
discard vrt data received before context