#168 allow to globally configure mappings using @GlobalMapping

I had to move ```@Mapper``` and ```@MapperConfig``` to ```core``` and ```core-jdk8```, as they now require ```@GlobalMapping```, which in turn requires ```@Mapping```... 
Does this take sub-types into account? I.e. will this configuration be applied when mapping e.g. a `SubVehicleDto` derived from `BaseVehicleDto`?