Call analysis improvements

[ds5678]

I made a few more improvements to improve the output:

• All primitive types are correctly resolved now.
• Concrete generics are handled properly so that they no longer show up as unknown methods.
• Lists of concrete generics are consolidated into their common base type.
• PE exports no longer get counted as unknown calls.

Possible improvements for the future:

• The Type field of CallsAttribute and CalledByAttribute sometimes attempts to reference an inaccessible type such as System.ThrowHelper or a type from an unreferenced module. Adding a string TypeName field might be desirable to handle these edge cases.
• The Member field of CallsAttribute and CalledByAttribute currently just contains the member's name. A full signature might be better for removing ambiguity.
• Generic types in the Type field currently don't have type parameters. It may be desirable to retain that information and use it to fill those parameters where feasible.

[ds5678]

I implemented a system for verifying that a type is accessible. In the event it isn't, TypeFullName is used instead. I do not plan on implementing any of the other potential improvements in this pull request.