Enforced text input for the look command in menu_login, as per #605.
Made a different regex for #605.
Added more verbose error logging to cmdset loading.
Deprecated the code= keyword of contrib/menusystem - this is replaced with a callback keyword where a function object is supplied rather than a code string. Code still works, but will give a deprecation warning in log. Cleaned up the code and fixed dynamic yes/no allocation. Should handle the remaining issues of #596.