Update gitlab.io links to be buildgrid.build + update FAQ link
Since Adam got rid of the re-direct with buildgrid.build, this MR changes the links in README.rst from buildgrid.gitlab.io to buildgrid.build. I mistakenly thought we didn't have an FAQ so removed reference to this in my first commit, however it turns out we do...so I've added it back in and updated it to be the correct link.
Changes proposed in this merge request:
- Update gitlab.io links to be buildgrid.build.
- Update the FAQ link.
Follow the new links and check they go to the right places.