A quoted string is a string enclosed in '"':s. This makes it clear
where the string begins and ends, avoiding ambiguity with whitespace.
After the config file has been loaded, the '"':s at the beginning
and at the end of the string are erased. Querying the config value
with config_get_string() will return this de-quoted value.
For example, if the config file reads 'my_string="test""', the actual
string will be 'test"'.