Don’t add self._single_wildcard_char and self._multi_wildcard_char to se...

...lf._valid_input_chars and self._pinyin_valid_input_chars

This is because the wildcard characters can be changed with the setup
tool at runtime. If they are added to the string of valid input
characters, the old wildcards would need to be removed from that
string if the wildcards are changed. But the wildcard character may
have been in that list already before it was added as a wildcard
character. In that case, only one instance of the old wildcard
character should be removed from the string of valid input characters
if the wildcard character is changed. Replacing the wildcard
characters in the string of valid input characters when they change
seems more confusing that not adding them to that string in the first
place.

Therefore, I do not add the wildcard characters to the string of
valid input characters anymore, but that means that when checking
whether a character is a valid input character

    if c in self._valid_input_chars:

is not enough anymore, now one needs

    if c in self._valid_input_chars + self._single_wildcard_char + self._multi_wildcard_char:

That seems less confusing than adding the wildcard characters to
self._valid_input_chars and replacing them there when they change.