added numberOfPipelinesPerProject option to GitLab service config

[ntamas]

This pull request adds a new configuration option called numberOfPipelinesPerProject to the GitLab service config, allowing the user to specify the maximum number of pipelines (builds) to fetch for a single project.

This will allow users to select a group of repositories (e.g., all repositories that are owned by the user corresponding to the key that the GitLab API is called with) and specify that the build monitor should show only X builds per project. When the builds are sorted by IDs (which is the case right now), this ensures that only the most recent X builds appear on the CI display. In our case, we use it with X=1 to show only the most recent build for a group of repositories being monitored.

[marcells]

Thanks for you PR! It will fix issue #64. But could you please extend the README.md with the new flag?

[ntamas]

Here it is. Actually, since the name of the option is significantly longer than the rest, it might be a good idea to shorten the name of the option. Feel free to propose a new name if needed.

[marcells]

Thank you! I like expressive names. ;-)