* Keep go and cc templates separate

Otherwise the last set of templates registered take proprity, so the Go
templates override the C++ ones

* Initial C++ validation code templates

* Make imported pgs package name explicit

* Test boolean C++ validation

* Add C++ wrapper template to make the build work

This will be removed in a later commit.

* Prevent regression by allowing failing TestResults

Instead of allowing any of the test cases from entire test handler to
fail without failing the test, require that test cases allowed to fail
be individually marked. This prevents errors from being masked while
allowing unimplemented tests to pass.

* Enable C++ validation for numeric types

The code for this was already mostly implemented in the template, but
now it is actually tested by the C++ harness.

* Add comments about the C++ harness macro