Adds a Gitea service with a CI runner at https://jungle.bsc.es/git/. The GitLab from the pm.bsc.es server is down. Given their setup depends on a VM machine that mounts an EXT4 disk over a GPFS volume and the dmesg messages show signs of corruption, I don't trust that setup. Additionally, the opaque administration of the VM machines doesn't help.
The instance stores all data into /var, which is backed by a single SSD disk for now. It is fast but it will eat your data eventually. We should move it to Ceph, so we have a three-way redundant storage.
Load times of merge requests pages are in the order of 400 ms, instead of the 2-3 seconds of GitLab.
I also fixed some problems with the website and added a link to the Gitea service on the top menu. Registrations a currently closed, but we can manually add new users.