Use latest build of V2 in the adapter

[CharliePoole]

The adapter repo holds binary files drawn from NUnit 2.6.4 in order to run NUnit tests. But NUnit 2.6.5 has already been released and NUnit 2.6.6 is about to be released. We should upgrade the files used in the adapter.

This can be done, of course, by directly updating the binary files we currently use, but a better approach may be to use a package to do it. The 2.6.6 release includes a package with the nunit.core and nunit.core.interfaces assemblies. We could use these and possibly add the nunit.util assembly to the package. A simpler approach may be to elminate use of the nunit.util assembly from the adapter. That's the approach taken by the v2 framework driver, which only uses the core assemblies. Using the core assemblies simply means that the AppDomain in which tests are run would have to be created by the adapter itself.