Context: https://github.com/xamarin/xamarin-android/pull/1343
> Trying to refactor `README.md` so it's more concise...based on the
> user's goal to contribute or provide feedback when visiting the
> repository.
If we're to make `README.md` shorter, then the contents of `README.md`
need to be moved *elsewhere*.
Reorganize the Documentation, taking inspiration from dotnet/coreclr
for general organization principals:
* Documentation/building: How do we build this thing?
* Documentation/guides: "Product documentation" which should live
"elsewhere", but we want here for sanity purposes.
In particular, the Build Process documentation.
* Documentation/project-docs: What is Xamarin.Android?
* Documentation/workflow: How do we develop this thing?