API BEHAVIOUR CHANGE: now all setDAC functions only accept ROC I2C
addresses. only the ROCs with the given address will be programmed.
This addresses the issue found by @ursl, mentioned in #271. Some
further code refactoring to make it cleaner and simplifying the DUT
access in case of programming all ROCs. Should be sane now, has
been tested with dummy DTB. Bumps pxarCore version to 1.7.4
Merge branch 'master' of github.com:psi46/pxar

Conflicts:
	CMakeLists.txt