Added specs for new resource types and fixed store accessor methods

Added a few new resource types (Credit Memo, Customer Deposit), enabled new resource type inclusion, and added tests for all new types added previously.

Also fixed store accessor methods so that if a potential store accessor method already exists, new methods are created that prefix the name with an underscore.

eg. "class" already exists for all objects of NSConnector::Resource.
When we try to add store accessors for field called "class", new getter & setter methods are created with the name "_class" and "_class=".