Some permissions updates

Specifically, it now checks if the user has permission to receive
updated books before doing those updates.
Renamed the permission in question to a much clearer name
"konseptbooks.getupdates" for clearity.

Also includes some JavaDoc updates and some comments.
Nothing major enough to mention specifically.
/konseptbooks -delete implemented

Will delete a book from the library based on the book in your hand.

Also, more permissions work:
- Now checks permissions when updating all players after books
  update in the library.
- Changed to the correct permissions name for the konseptbooks.user
  when referring to "getupdates" (was "read", the old, silly one).
Implementing book deletion from console

Very useful!  Well, somewhat useful.
Okay, it's just ...  I don't know, it seemed like a good idea at
the time.