gschem: Wrap remaining builtin commands using new actions.
gschem: Add a &repeat-last-action meta-action.

Rather than having repeat-last-command as a special symbol that causes
special behaviour of eval-action!, add a special &repeat-last-action
action with an associated name & icon.
gschem: Avoid infinite loops in &repeat-last-action.

Make sure that &repeat-last-action can't set itself as the last
action!