* hydra/modules/sysadmin/web.scm (static-web-site-mcron-jobs): Expect a
list of <static-web-site-configuration> records.
(static-web-site-activation): Likewise.
(static-web-site-accounts): Define using 'const'.
* hydra/website.scm (website-services): Adjust accordingly, using one
'static-web-site-service-type' instance for all of guix.gnu.org.
* hydra/bayfront.scm <services>: Adjust hpc.guix.info instance
accordingly.
* hydra/berlin.scm (%rsync-modules-for-backup): New variable.
<services>: Add 'rsync-service-type' instance.
* hydra/website.scm (website-services): Add comment about the Cuirass
and GWL web sites.
Factorize website services in a single (website) module so that they can be
hosted by multiple nodes for redundancy.
* hydra/website.scm: New file.
* hydra/berlin.scm: Use it.