added override for isplainobject in assettable

pertains to DAQ-647
pass reference to original isPlainObject

pertains to DAQ-647
more understandable asSettable isPlainObject names

per @ralphsmith80 recommendations

pertains to DAQ-647
Merge pull request #4 from siq/overrideisplainobject

added override for isplainobject in assettable