License issues

As described by @dscho there were some license issues in the projectors/converters. This pull requests adds the missing license headers for several files in the projectors package and fixes wrong licenses. 

@axtimwalde  could you please review the licenses of Volatile2dRandomAccessibleProjector, ARGBARGBDoubleConverter and ARGBDoubleARGBConverter. If everything is ok, you can merge the pull-request.