*Very* rough initial version of the capnp parser.
- Can parse schema.capnp, that is to say it gets to the end without an error. Does not, yet, resolve import.
- This is just a first pass and some primitives are not yet parsed (e.g. floats) and references to const are not done.
- An intermediate representation is created, probably needs work. A second 'pass' is needed to resolve type references, parse imports, resolve aliases (usings) and parse default values once their types are known.
- It's probably not even correct because it's currently based mainly on the Capnp schema examples, for correctness we'll probably have te scour the c++ parser and compare.
- There are currently no dependencies on this code and testing is, for now, done in a the Xxx_tests.cs file using xunit for now.
Add xunit nuget packages.
- It appears packages are committed to this repo, so I'll follow suit.
- If xunit is a problem because nunit is already used I can switch.