quick: Fix auto-commit on 3rd letter

When the user inputs 2 letters in Quick, we fetch the candidates.

If she presses a third letter, we should commit the first candidate and
keep the third letter as the first of a new input.

We were committing the first candidate, but losing the third letter, so
the user had to type it again.

This commit fixes it.
quick: Don't treat * as a wildcard

The concept of wildcards makes no sense in Quick. As such, we need to
treat the star key differently for Quick and Cangjie.
Don't clear the input for all commits

In some case, we want to commit a character but not clear the input.

This is desired for example when inputting a fullwidth character.

The proper fix is to only clear when needed, and not in the commit_text
method.
Drop useless method

This now doesn't do anything more than the parent method.