Extend project integrity to support reporting.
Start with 'checkproject' command.

Along these changes, the implementation of the first command line
enabled command is started. It's implemented as 'verb' called
'checkproject' and resembles the `CheckProject` task of the nant task.

It's still early and heavy WIP, since following stuff needs to be ironed
out before it starts to report usable things:

* Make both the whitelist and the 3rd party libs path configurable (via
  options and via config file for whitelisted gac assemblies)

* Make the `Check` and `Report` methods of `ProjectIntegrity` stop on
  first error.

* Enhance the reporting with more (sensible) report messages