vizualisation: Add tf-main vizualization script

Add `tf-a-main-results.{bash,plot}` to fetch test results from a Jenkins
build of tf-main and vizualise them. Update README.rst with usage info
for the new script and plot description.

Change-Id: I837a2dcb4cd3247b24ba9eec6557699e9a75e9c2
Signed-off-by: Nathan Dunne <Nathan.Dunne@arm.com>
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
7 files changed