Load files from libs into repo.

Repo is a hash directory contains all ebook files. Each item in
repo resides in a directory whose name is the file's fingerprint.
In the item direcotry, two files could be found, "meta" contains
json format attributes about this file, "text" contains ebook
content in text format.

After update.py update all files from libs to repo, it will create
a "queue.<timestamp>" file in repo directory. This file can be
used for next operation indexing into search engine.