Disable building Qt5Json, remove Qt4 dependency
Disable building Qt5Json, remove Qt4 dependency

We may want to add back in support for building a Qt4 client library,
but at this time just disable Qt5Json as it is no longer used.

Change-Id: Ic28013c70a31358beb70cbcfafe5cb99942291ad

OpenChemistry/molequeue,OpenChemistry/molequeue,OpenChemistry/molequeue