updated many docstring. mostly minor changes.

according to http://www.apache.org/legal/src-headers.html#headers, there
should be no copyright notice in the header.

- added zero-version variable in zero-framework.el

- 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.

let zero-table base on it.

basic things work.
pagination not added yet.

this is largely working, only waiting for integration with zero-panel.