Add `G` (jump to end) keybinding

[rwev]

Fixed. Unfortunately as a side effect, I had to remove the G (jump to end) vim-style keybinding because it isn't compatible with how the displayed item boundaries are managed.

Right now, the beginning and end boundaries should always have a difference between them equal to the height of the viewport, curses.LINES - 2, Otherwise, changing the book selection to one with more chapters would result in truncation.

Jumping to the end of the list and showing the last curses.LINES - 2 items may result in the beginning index becoming negative, depending on the length of the list, which would break the ListWindow.draw routine and further boundary changes.

Originally posted by @rwev in #5 (comment)

[jajpater]

I gave a solution that binds L to jump to the bottom of the screen, the last displayed item. Now we stil need a solution that jumps to the bottom of the entire list that is bound to G.