remove some un-clear definition in book model and add book language
Merge branch 'develop' into feature/multi-language-for-book

Conflicts:
	book/forms.py
[WIP] add language prefer settings

rewriting it to angularjs base
use basic filter for book admin
fix foreign key select in book admin
rename api_view to api_list_view for clearer meaning
reverse language settings back to normal form
active user menu when visit favorite book
add header for language setting page
add category for publish new book form
remove all things related to book type and chapter type
remove wrong commit in profile
split step of filling information for publish new book
fix not found template after remove book type
replace tab by 4 spaces
finish fix and change copy book feature

allow to visit book by source's thread id
split steps for easier to understand feature
add back factory create book before app
add lettuce django port config
add back class notifications for notifications
fix post new chapter after adding language