Adhere to CRP C++ Style Guide

https://github.com/ComputationalRadiationPhysics/contributing/blob/master/codingGuideLines/cpp.md
What this project does not do:
- [ ] doxygen ```@file ...``` documentation
- [ ] wrap at line 80 (we do 120-ish)
- [ ] no code alignment
- [ ] indentation inside the deepest namespace
- [ ] spaces around parameters in single-argument functions
- [ ] trailing return type declaration (for lambdas, AFAIK ```auto``` is never used for function defs)
- [ ] function/method specifier on newline
- [ ] newline after and before ```(``` / ```)``` of function signature
- [ ] parent classes are indented and placed on a new line
- [ ] constructor ```:``` on same line (we do newline)

What this project does not do consistently:
- [x] copyright notice in every file
- [ ] namespace structure (per dir, see #82)
- [ ] lowercase foldernames (e.g. ```IO ```, ```ADIOS ```, ```HDF5 ```)
- [ ] indent of 4
- [ ] camelcase (some non-exposed internal functions use underscores, on purpose)
- [ ] closing of multiline comments on newline
- [ ] spaces around binary operators
- [ ] newline on each ```,``` in function signatures
- [ ] single spaces around ```&``` (reference) and ```*``` (pointer) (most often the left one is omitted)
- [ ] initialization over assignment
- [ ] indented ```case``` statements
- [ ] prefix ```T_``` for template parameters
- [ ] case for template names
- [ ] each template parameter is on a separate line
- [ ] spaces around parameters in template instantiation (we try hard, but might have missed a few)