Support for Net40client

I've added support for .net 4.0, in order to do this is had to update the `portable` and `net45` projects:

Portable changes:

- downgraded target from .net 4.5 to .net 4.0
- update packages config

Net 4.5 changes:

- moved the csprof file to `ext\Net45`
- added links to the required files
- added Castel.Core and Newtonsoft.Json to the packages.config, this is now possible because the .net45 project has it's own packages.config file

Net 4.0 project has more or less the same changes as the .net 4.5 project except the fact that I've added some more links to files

Other changes:

- I've update a failing integration test