Resolves #676.
Make its internals visible to the `powershell-tests` assembly, and use its `MyHost` and `Listener` classes instead of facades.
This initialization was moved out of the native host and into the managed host, so the same setup must now be done before tests.
- Pester source code moved to `test/Pester`, deleted `ext-src`. - Pester tests (.ps1 files) moved to `test/powershell` - xUnit tests (.cs files) moved to `test/csharp` - Third-party script test moved to `test/shebang`
Andrew Schwartzmeyer