[mdoc] consolidated dropns and dropns-assemblies into a single parameter.

Based on pull request feedback, this is a simpler usage, and meets our required use-case. A sample version of this parameter would be: `--dropns MyUnifiedAssembly=MyDroppedPrefix`
[mdoc] Framework owner tests

Modified makefile and added new test class file.

This is to support the ability to run an mdoc update with multiple versions
of an assembly that may have different members and classes available.