Add an option to mention a single project/repo

Today, if you want to parse a GitLab subgroup, you only need to specify its ID in the command line:

python3 ip_check.py -g <Group_ID>

For a project, we need to mention a file which will contain one line with the ID and the path to the repo.

To be consistant, I will suggest to have the -p option to reference the ID of a project and have another option, for example, -pf or -pFile to mention a file with a like of projects.

As a subsidiary question: why the ID of a group is enough when the ID of a project is not? There is certainly an issue with GitLab?

Thx a lot