Move module doc to class doc so we can use it in the automatically created steering file

Change docstrings to be more sensible

changed member variables to private: _errorMessages, _dumpParameter, _dumpSteeringFile

removed abspath from macroFile and compactFile because otherwise the default values break error checking

See example/steeringFile.py and DDSim/Helper/Filter.py for examples

see the steering file or the ConfigHelper/Action docstring for an example for CaloPreShowerSDAction

use absolute path for steering, compact and macro file
remove magneticFieldDict because no longer used

in command line for example "--action.mapActions 'tcp TPCSDAction'"
or see example/steeringFile.py

ddsim: remove some commented lines, add dump[Parameter] flag to just print the configuration parameters

* Move DD4hepSimulation et al into python module DDSim, needed for proper
  importing

* Can now control magneticfield setup, gun, particle handler, output via command
  line.

** added ConfigHelper and daughter classes implementing these options
   DDSim/DDSim/Helper, easily extensible to additional features

** also easier changing of these parameters via steering file See
   example/steeringFile.py

*** No more functions, no more "global GeV"

** --help string can be given by using @property, see e.g. Helper/Output.py

* added optional argcomplete, allows command line "tab"complete for all command line options (and values!)
  Needs argcomplete (sudo pip install argcomplete), bash completion and bash (or zsh).
  and 'eval "$(register-python-argcomplete ddsim)"'

* move import statements to reduce startup time until "--help", mandatory to
  reduce latency for argcomplete

Move DD4hepSimulation.py and RunProg.py to DDSim folder
Rename RunProg.py to ddsim
Add cmake install for DD4hepSimulation to lib/python, ddsim to bin which is already in PATH