Merge branch 'update-task-plots' into 'master'

Update the task plot scripts to include new tasks and subtasks.

Also fixes an issue where gaps between successive tasks of the same type
were not seen as these were joined (for plotting efficiency I guess).
A gap is now seen.

Also change the colour handling so that the task/subtask types are
easier to differentiate.

Fixes issue #260.

See merge request !311