Improve Docstring and comments of the losscalculator

Both docstrings and comments need to improve in all the losscalculator files from the aspects below:

1. Typos
2. Meaningfulness
3. Coherence

Some other things to fix are as follows:

in damage_calculator.py:

1. line 44 must change to result.gpkg and not csv, because of line 45 in which the default output format is gpkg and not CSV.
2. In the Docstring of the damage calculator, we should poit of the manual.md for more info.
3. Have either the word 'choice' or 'option' for the possible options of some inputs in the argparser.
4. Make sure that user gets an error message when using options -c and -f at the same time.
5. What happens with -o given as 'CSV' but no -r given?! Results will be written to gpkg!
6. Why option -a and geopackage output format do not work together?!