change TargetFrameworkVersion to 4.0 in order to be able to run Concordion specs with NUnit 2.6.3
fix loading of config files: use Assembly.CodeBase instead of Assembly.Location -> all Spec tests pass with NUnit
 -> all Spec tests pass
rename project Concordion.Integration.NUnit to Concordion.NUnit
Merge remote-tracking branch 'origin/master' into Documentation