Flent v1.2.0

Changes since v1.1.1 include:

• Add support for the irtt binary (https://github.com/peteheist/irtt/)
  for isochronous UDP latency tests. If irtt is available in $PATH, it
  will be preferred over netperf for UDP RTT tests and over D-ITG for
  VoIP tests. This means that UDP latency tests will no longer use more
  bandwidth as the RTT decreases, and VoIP tests are easier to setup.
  Many thanks to Pete Heist for writing the irtt tool.

  As part of this change, a generic facility for runner preferences has
  been added, which makes it possible to define a test in terms of
  higher level functionality and let Flent pick the best available
  underlying tool to run the test. For now this is only used in the
  cases mentioned above for irtt.

• Add a configurable option for overriding the colour mode for plots.
  This makes it possible to change how colours are assigned to different
  data series.

• Improve handling of multi-value options between batch files, rc file
  and command line. This means that multi-value options can now use both
  comma and semicolon as separators in the batch file, and values can be
  quoted to prevent splitting.

• Drop compatibility with matplotlib versions earlier than 1.4.2. Using
  older versions resulted in spurious errors anyway, and it is too much
  backporting work to support them properly.

• Fix batch mode logging to make sure a log file for a batch run only
  includes log lines from that run and not previous runs.

• Fix several bugs in the plotting and runner code.