Additionally remove a lot of 64-bit-specific configurations
(Debug64/Release64) as well, and just make the default configurations
(Debug/Release) be 64-bit.
Unify a lot of code related to how to load test assemblies.
This resulted in adding a couple of test assemblies to monotouch-test when executed on macOS (this was a bug), and this also required adapting some of those tests to work correctly on macOS.
This fixes a problem where the build from the different projects could stomp
on eachother in the obj/bin folders. It's technically possible to make this
work by setting up custom [Base][Intermediate][OutputPath] properties in the
project files, but the simplest solution is to just make sure there's no more
than a single project per directory.
Rolf Bjarne Kvinge
Sebastien Pouliot