Add gitlab documentation api parser, add models, some logic changes

[derjones]

Hi,
I wrote a parser to parse the gitlab api v4 documentation page and generated the models exactly like the documentation.

Take a look.

Cheers

[derjones]

Hey,
I updated the models. Now the current gitlab api is completely supported.

Thanks, jonas

[derjones]

If you don't want to merge these changes just write me.
Then I will keep it forked and publish the project on a different name.