book and book-delete are now case-insensitive

Changed storage of book list to use associative array with lowercase label as key, mixed case label as value.
/book-list displays the original case form of the book label as entered in /book-publish, and /book and /book-delete can use any cased variant of the label.

Adjusted a few commands to accommodate input mistakes
Rearranged command readout when admin uses /book without arguments. Also changed colors to be easier to read.