Flash/beep detection improvements, customisable test sequences and various bugfixes

NOTE: Not backward compatible with JSON metadata files generated by the
test sequence generator in earlier versions (due to pulse detection
enhancements).

• Enhancement: Flash/beep detection algorithm improved. Test sequence
  generator modified to add extra metadata fields that describe the duration
  of the beeps and flashes in the test sequence.
• Enhancement: Added ability to add custom labels and colours to generated
  test sequences.
• Enhancement: Added ability to control how long capturing lasts using
  --measureSecs command line option
• Bugfix: Failure when measuring not using LIGHT_0 input
• Bugfix: FFMPEG was adding timing offset to audio (relative to video) in MP4s.
  Added offset via command line options to compensate.
• Bugfix: exampleCsaTester.py was providing incorrect presentationStatus
• Bugfix: Corrected detection of ffmpeg in test sequence encoding script

0.2 : Added TV Measurement

This release adds the ability to measure synchronisation timing of a TV.

Note: This code requires pydvbcss 'master' from 6 Mar 2015 or later, or release 0.2 or later.

Initial release

Initial release of this measurement system project.

Intending to follow very shortly with an update that adds TV measurement.