Warn when user wants to configure properties in way it is not fully supported

I was quite surprised that even i switched on checkstyle.configurationFile changes were applied for all file. I though this is sputnik error but it seems to be lack of support. I added some validation so nobody won't be surprised :)
It's not pretty now. It would be better if you would just extract building method into small method so that public build method calls two: internalBuild and validate