save settings from untrusted config files in a separate configparser
This untrusted configparser is a superset of the trusted configparser,
so that interpolation still works.
Also add an "untrusted" argument to ui.config* to allow querying
ui.ucdata.
With --debug, we print a warning when we read an untrusted config
file, and when we try to access a trusted setting that has one value
in the trusted configparser and another in the untrusted configparser.
35fb62a3a673d5322f6274a44ba6456e5e4b3b37 0 iD8DBQBEYmO2ywK+sNU5EO8RAnaYAKCO7x15xUn5mnhqWNXqk/ehlhRt2QCfRDfY0LrUq2q4oK/KypuJYPHgq1A=
2be3001847cb18a23c403439d9e7d0ace30804e9 0 iD8DBQBExUbjywK+sNU5EO8RAhzxAKCtyHAQUzcTSZTqlfJ0by6vhREwWQCghaQFHfkfN0l9/40EowNhuMOKnJk=