Allow configuring Axii to define a set of code hosting servers for which SSH or HTTPS should be preferred

This is a take on how to handle the problem of choosing a connection method for cloning, i.e., HTTPS vs SSH.

I think that HTTPS should be the default connection method since it works more robustly and without prior setup (generating key-pair).

We could then allow configuring Axii, for example via:

axii config --global code_hoster_connection_method:git.h2t.iar.kit.edu ssh
axii config --global code_hoster_connection_method:github.com https

During cloning, Axii would just use what is configured, or HTTPS if nothing is configured.

Additional considerations:

We should also allow for setting the preferred connection method in the module config
Of some known servers, SSH fingerprints can be stored to overcome the issues with ssh prompting for allowing the initial connection
Should work well with axii w verify. I.e., Axii should report configuration issues if for example some Git repository uses HTTPS even though the connection method was set to ssh using axii config