Merge DomainInformation and SubGrid

Fixes issue #416 

 - move Selection to PMacc
 - merge DomainInformation into SubGrid
 - remove SimulationBox from SubGrid

I tested this with a 128/512/128 4 GPUs LW moving window simulation - images looked good.
~~Note that there might be some documentation still missing.~~
I am not sure if it is good to return a reference. IMO this part is not time critical and return a copy is more clean.