Add parsing of references and project references to the project file parser

[daveaglick]

The project file parser handles several types of project file information, but it does not include support for parsing project assembly references or references to other projects. This type of information can be helpful if, for example, you're trying to fine-tune NuGet packing based on referenced projects.

[gep13]

@daveaglick I have manually merged the PR that you created, but your work has been attributed correctly, thanks!