Disables the previous/next arrows on pdf books on the first/last pages respectively
Fixed js coding style for pdf arrows toggle
Display:none arrows in disabled state
Moved jquery event handling to parent since hidden elements do not get events attached
Revert last commit
Merge pull request #1057 from edx/usman/lms-1114-pdf-arrows

Disables the previous/next arrows on pdf books on the first/last pages