Fix a bug where prevSpecial(x, false) would fail

Copy+paste error :)
nextSpecial calls itself when it found a special frame but is supposed to skip them.
prevSpecial also called nextSpecial instead of prevSpecial in that case,
leading to getting stuck on one special frame if the previous one was a debated one.
(This was not visible on the website since the boolean parameter was never used.)
Add next/prevDebated functions.
Add prev/nextDebatedFrame functions to navigation

(Not used yet)
prev/nextSpecialFrame on shift + arrow keys

This completely fixes #83.

(Also, some re-indenting in the key handler. Best viewed in "ignore whitespace" mode.)
Fix #123: enable/disable next/prevSpecial buttons

respecting the "pause on debated frames" checkbox.
Update buttons when "Pause on Debated Frames" changes

because this might need to enable/disable the previous/next-special buttons.
Rename "timer" to "playforward"

implementing the TODO in ayop-navigation.
Reformat ayop-navigation.js to untabify.

Sorry :( better now?
Merge pull request #125 from lucaswerkmeister/pullreq-125

Fix 83, fix 123, minor other stuff