give all gradients in viz output a unique ID to fix a bug where some legend sometimes disappear.
allow user to control path to createPPRMat.m file in case they run makeRequiredPPRFiles.py in a different directory (e.g. from the root of the release).
Merge branch 'master' of https://github.com/raphael-group/hotnet2
add hotnet2 to path in createPPRMat.py in case it is run from bin/