- handle fetch more in page down function.
- let build-candidates sync version support fetch-size param.
- adjusted some debug log
- tested zero-pinyin and sync and async mode, both works. I can't feel the
  difference.

replaced the command remap for delete-backward-char.
because some major mode bind DEL on other command.
zero-mode should always allow DEL for preedit-str editing.

dbus based sync and async api both works.
- added error handler for dbus client in emacs lisp.
- use lexical-binding for all files
- added M-x zero-reload-all this will byte compile and reload file files.

easier to read and eaiser to write.

make partial commit work with zero-pinyin.el
added a few "virtual functions" in zero-framework.el
removed SPC key in keymap, just use self-insert-command remap.

add auto commit first candidate or preedit str on punctuation insert.
add default binding C-. for zero-cycle-punctuation-level

let zero-table base on it.