Use pandas instead of default csv python module

[ChrisRBe]

With the current implementation, output files are written by the default csv module. This means that any floating numbers are printed with "." as decimal delimiter by default.

To improve the localisation of this script with regards to US and EU decimal delimiters, pandas provides better support for this kind of differentiation. See also pandas.DataFrame.to_csv for the API definition.

decimalstr, default ‘.’
Character recognized as decimal separator. E.g. use ‘,’ for European data.

To be further investigated if pandas or python supports automatic localization detection to make this location based.

Implementing this feature/rework should help resolve also issues reported in #692.