Improve metrics processing

[t00sa]

A few improvements:

• [ ] remove dependency on matplotlib from core fab. Maybe move the functionality into a dedicated command line tool?
• [ ] some phases do not appear to be tracked beyond bulk statistics, e.g. psyclone. Include the ability to track on a per-file basis.
• [ ] output data should be partitioned to split out summary statistics from individual data points
• [ ] fab command should include the ability to generate a text summary at the end of each run