- zero-framework.el and zero-pinyin.el when updating zero-fetch-size,
  should update it to

    (max (length candidates) fetch-size)

  because service can return more than asked and it still counts.

- zero-panel.el add hints support and use it for pass has_next_page,
  has_previous_page indicator.

- 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.

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.