#3 - Crichton refactoring resource dereferencer

@fosdev @sheavalentine-mdsol @chad-medi @jcarres-mdsol 
This PR adds resource dereferencer class (later to be renamed to Resource class). It represents entire resource descriptor document. It responsible for self-dereferencing and registering descriptors available in it. Descriptors are represented as DescriptorElement objects. 

This must be merged after #147 

Please review and merge!