Refactor CT->RT Vector, General Half-CT Mapper

- follow up to #335
- satisfy @psychocoderHPC at
  https://github.com/ComputationalRadiationPhysics/picongpu/pull/347/files#r11628952
Fix Interface To linearIndex
First draft

- still not compiling ;)
Fix all compile time errors

- add in Plugin Controller to test compile
Single GPU first running

- (fix) compiles and runs without crash
- (bug) does only find a subset of particles
- (bug) last buffer not flushed -> increase with each notify()
Fix Default Value and first results

- (Fix) Default value now set on 2D and 3D dBuffers
- (Test) SphericMapper written in a more intuitive way
- (Fix) Zone for Particles set to right value in
        calcPhaseSpace() zoneCoreBorder
- (Bug) Still only ending up with 144x1024 instead
        of 128x128x12 particles in phase space
Use Lambda for Assign again

- lambda fixed since eef746a
- still only 144x1024 particles detected
Multi-GPU draft

- needs host::foreach fix (pull comming)
- resets spheric mapper changes (separate pull)
- adds some hints/warnings/todos to FieldEnergy.tpp
- adds 4GPU example
Remove Gather and stay with local result

- Correct SphericMapper: Wrong Rebase result (k3diff)
Add Multi-Phasespace Capability

One can create multiple phase space plots in the same run now.
Add --ps_e Analyser in cfgs

- add PS analyser examples
- remove old files
- fix typo in createParameterSet, choose a word that sounds less horrible
- remove hdf5.compression flag (outdated)
Momentum_Range: transform to desired units
Use new Cell2Particle interface

- PhaseSpace: add charge with CounterShape for now
Documentation and Defines

- public defines for convinience
- more doc
- prepared outsourced output
- SphericMapper: still a wrong line from rebase - corrected
Output draft

- multiple txt files: done (missing units)
- serial splash: draft
- parallel splash: missing
Update Attributes with correct values

- fix operator template for splash implementation
Fix all Splash compile errors
Add PS in 16 GPU cfg file
Create Reduce MPI_Comm once

- move creation of mpi::Reduce to moduleLoad()
- create a new MPI_Comm with ranks of the root processes of the plane reduces
Add Parallel Splash Output Capabilities