Create README.md

create .md file
add MappedBufferIntern

- add MappedBufferINtern which is a DeviceBuffer based on cuda mapped memory
- cleanup all interfaces which hard use DeviceBufferIntern to use the interface of DeviceBuffer
- extend interface of Devicebuffer
Prepare global Environment singleton for PMacc
Edited after review-comments

-modefied Environment.hpp
-removed most of the forward declarations for class Environment
-removed some .tpp files
Fix GridBuffer Destructor

In case the GridBuffer is not running for the whole simulation,
we have to make sure that the transaction dependencies between the
allocated memory (host, device, mapped) and the GridBuffer
will be sheduled right.
Merge pull request #1 from ax3l/topic-bufferRedesign

Fix GridBuffer Destructor
change annotated points
add option to check mapped memory

- new option --mappedMem
- use cudaHostAlloc if --mappedMem is enabled
delete old comment
add yml documentation
simplify extension param file
correct a_0 in Bunch documentation
change kernel for dimensionless usage
correct mistake - removed bunch
Merge pull request #173 from psychocoderHPC/feature-mappedMemoryTest

add option to check mapped memory
Merge pull request #169 from psychocoderHPC/topic-bufferRedesign

add MappedBuffer
Merge pull request #176 from PrometheusPi/issue7singleParticleRad

Documentation for SingleParticleRadiationWithLaser
fix TaskSetValue bug

- old version of TaskSetValue create out of memory access in some cases
- cleanup code of TaskSetValue
- delete virtual destructor of SuperCell
change annotated point from github
solv rebase conflicts