issue-37: throw an exception when passing a description object to RT.registerType that is not an object or that is missing a memembers element.  Also, allow a missing constructor member by defaulting to the Object constructor.
issue-37: throw an exception when passing a description object to RT.registerType that is not an object or that is missing a memembers element.  Also, allow a missing constructor member by defaulting to the Object constructor.

chbfiv/fabric-engine-old,errordeveloper/fe-devel,chbfiv/fabric-engine-old,chbfiv/fabric-engine-old,chbfiv/fabric-engine-old,errordeveloper/fe-devel,chbfiv/fabric-engine-old,errordeveloper/fe-devel,errordeveloper/fe-devel,errordeveloper/fe-devel,chbfiv/fabric-engine-old,chbfiv/fabric-engine-old,errordeveloper/fe-devel,errordeveloper/fe-devel