use fuzzy_flag param in a new method instead.
added GetCandidatesV2 method in service interface.
use this new method in zero-el.

- added FuzzyFlag property.
- updated zero-pinyin.el to support zero-pinyin-fuzzy-flag variable.

- CommitCandidate allow save phrase and user_freq in user db.
- bugfix: GetCandidates SQL query ORDER BY field fixed.
- bugfix: fix a memleak in on_handle_get_candidates()
- minor bugfix: fix variable name in meson.build

this method allow user to delete candidate so they won't appear in
future queries.