adding new class to work with Library, new views for books, new templates

changes in __init__.py:
- route to library
- route to add book
- route to edit book

changes in views.py:
- Library class, it will be used to work with books and all other stuff
that relates to this
- view to add book, accepts following parameters:
- - - category (will be automatically generated from available
categories)
- - - author, automatically set to current used
- - - title
- - - amount
- - - deleted, or better to say, book status, by default it is set to
1, e.g. Active

- library view, is used for the following purporses:
- - - displays all available books in library
- - - allows to edit, delete this books
- - - has link to add new book
- - - has field for book search

- new templates for library and book adding