Changes to support Mono:

- Add support for building against .NET 3.5.
- Add support for building against .NET 4.0.
- Add assemblies to GAC to validate they install properly.
- Add execution of console sample as a test.
- Update test suite to only run DbConnection related tests on Mono.
- Update test suite to use connection string builder to avoid malformed
  malformed connection specs, an issue with Mono and the hard coded
  scheme that previously existed.
- Add nunit-console to the list of dependencies installed.