Generic exiftool parameters -G and -n are hidden

[nitmws]

The functions execute(*params) and execute_json(*params) allow to set exiftool parameters.
Unfortunately the documentation of both functions doesn't mention that two exiftool parameters are set in a generic way (with the -common_args parameter as a kind of prefix): -G and -n (see the start(self) function of the Exiftool class).
The confusing issue is: this presetting of -G overrides other settings of group families in the params of the two execute functions, like -G1 to get more granular group names of the tags. Adding -G1 to the params does not show the exiftool family 1 group names of the tags. And the why is not documented.

[sylikc]

I'll work on some of this documentation when re-working the class sylikc#10