refactor: prefer systemd sockets over socat

- Document preferred method for socket use depending on use case;
- Fix Github web-flow key;
- Standardize naming of services;
- Use sys-ssh in ansible formula;
- Start services conditionally with Qubes Service and evaluated by
  systemd ConditionPathExists= instead of installing on a per qube basis
  with rc.local scripts;
- Change Qusal services to "qusal-" prefix instead of "qubes-" prefix.

Fixes: https://github.com/ben-grande/qusal/issues/80
Fixes: https://github.com/ben-grande/qusal/issues/79

salt/sys-git/files/server/rpc/qusal.GitInit

@@ -15,6 +15,7 @@ if ! command -v git >/dev/null; then
   die "Command not found: git"
 fi
 
+## TODO: subdirectory? dir+repo
 untrusted_repo="${QREXEC_SERVICE_ARGUMENT}"
 
 if test -z "${untrusted_repo}"; then