Merge pull request #220 from grundler/master

small bug fixes
Cython interface: allow access to setExternalClock and setClockStretch
Add setExternalClock and setClockStretch to Python CLI, bump version.
Rename Python Interface pixel class member from "roc_id" to "roc" to be
consistent with pxarcore api definitions.
new parameter for pretest
improve and parallelize setcaldelvthrcomp
remove serial
changed error (range) to be half of full range
removed FLAG_FORCE_SERIAL from scurves; still not 100% OK
work in progress
Merge branch 'master' of github.com:psi46/pxar
syntax compliance