Add configurable verbosity

Some error and warning messages, in particular "Search failed.  This means there is unmatched expression somewhere or we are at the beginning/end of file." are too long to be displayed on a single minibuffer line in a non-maximized frame, making the buffer shift upwards when point hits an unmatched paren, which can be quite distracting. A solution would be to add a verbosity option to suppress those messages or replace them with less wordy versions.