- SignatureParser -> DocumentationSignatureParser
- GetSignaturePart extension moved to DocumentationSignatureParser
- Inverted a condition
- Added a clarifying comment about generics

To let it build on mono

And add comments clarifying their behavior

There were two issues:
- Nunit doesn't like assertions inside of a TestCaseSource method.
- On mono, the test infra failed to resolve the new assertion attributes

- Allow parsing a signature without a member type prefix
- Allow parsing a member without a type name
- Allow matching multiple member kinds
- Rename some public methods to more closely match linker terminology
- Add a few more tests for edge cases

- License headers
- Don't use string interpolation
- Don't use extension method for GetSignaturePart
- Remove unnecessary nullable context
- Remove unnecessary IndexOf