refactor cudaEvent usage

- add `CudaEvent` which is a wrapper for cudaEvent_t
- solve problem that `cudaStreamWaitEvent` was called to often
- EventStream: add function `waitOn()`
change github anotations

- fix documentation typos
- change interface from copy by value to const reference where CUDAEvent is used as input parameter
move enable disable section for Score-P

- delete comments for enable/disable tracing in MySimulation.hpp
- add comments for enable/disable tracing in SimulationHelper.hpp
move step marker comment
added scorep --user flag to enable manual instrumentation
New scorep configuration for titan.
Inserted selective tracing.
Merge branch 'fw-titan-scorep' of github.com:winklerf-zih/picongpu into fw-titan-scorep