Allow to specify the group used in udev rules

[lbeltrame]

Is your feature request related to a problem? Please describe.
Not all Linux distributions use plugdev for groups allowed to access input devices. openSUSE, for example, has an input group.

Describe the solution you'd like
Keep plugdev as default, but allow changing this in a configure call.

Describe alternatives you've considered
Replacing the group manually before installing, but for any distribution doing packaging that would be probably extra effort, and potentially error prone.

[nirenjan]

@lbeltrame, can you try the feature/custom-udev-input-group branch and see if it works as you intended? If this is OK, I'll merge it to the master branch.

Thanks for the report.

[nirenjan]

I forgot to mention, I've updated the INSTALL.md file in that branch with the instructions for customizing the input group.

[lbeltrame]

The file is correctly generated, as far as I can see. Thanks for the prompt adjustment!

[nirenjan]

Fix merged in master branch.