Update book viewer features

Styling of sidebar contents
Add modal for adding comments
Auto-resize of navigation bar
Get data async and initialize in a callback
Update book viewer

* Disable comment interface for anonymous
* Resize Thumbs section to avoid showing partial thumbs
* Center Thumbs section arrows
* Fade effect for image loading
* Set title of book
* Style images based on proportion
* Set fullscreen button to toggle mode, place it on header
Cleanup and function descriptions
Comment button style
Update Book Viewer

* Add a progress bar to indicate the global position in the book
* Show always the comment button, with less opacity
* Unify the navigation functions to move the selected window and wrapper