Defaults should not be set again in the configuration

[lkiesow]

If a configuration has a default value, it's good practice to have it commented out and not set again so that users can easily identify which options were set and which werent. Right now, we don't do that:

emissions-api/etc/emissionsapi.yml

Lines 13 to 15 in 5113ff9

	# Number of parallel workers preprocessing the data
	# Default: 1
	workers: 1

This should look like

# Number of parallel workers preprocessing the data 
# Default: 1 
#workers: 1 

[shaardie]

We could also remove the defaults from the code and only distribute a configuration file with reasonable defaults set. Then all values are in one place. Currently defaults are in the code AND described in the configuration file which is more error prone.