Update the pull-request template so that it can be used to view or create pull requests
Add a form to create pull requests
Rename the fork property to something a little more understandable: is_fork
Refactor the project to reduce code duplication

For a lot of endpoints, the logic is the same for projects and forks, we
should thus rely on the same logic while preserving the different URL
and be able to adjust our logic according to if we are on a project or
a fork.
Adjust the link to create pull-requests in the repo_info template