Added core, Domain update

Added a core to Pnatter
- in the core will come easy to use classes for the project
- first class, options. Is usefull to make a construct accept an options
array

Added the IMapperAware interface
- used to tell a mapper that the entity wants to be injected with the
mapper
- for easy use, implement the IMapperAware. Then you can use the
MapperAware trait to get started

Mapper now implements Options

MongoDbMapper and SqlMapper, now know by default which hydrator they
need to use