Implemented the missing config_to_X methods

Now the commandline string for all steps are built. Also the file
and environment variables are writte / exported for all steps.
Removed the old version of config_to_command
Bugfix in parsing integer and float values.

The problem was, that I was not converting the strings to ints and floats.
That made an opentuner assertion fail.
Fixed a problem of None values in input file.

When the input file did not have a value for a specific field, it could
crash the script. I now check at parsing for None values and set the
according strings to an empty string.
Added some more nice feedback-output.
Running again

The script now runs again for a simple input file. It produces results with the run time
of the given binary.
However, timetags are not taken into account so far.
There might be lots of bugs in there.