Image event listener & Translation mode fixes

* Chrome's mousemove event fires even when the distance moved should be equal to zero. This was interfering with image clicks while drag scrolling was enabled. The script has been updated with checks that make sure the distance is not equal to zero and that no movement has occurred before any mousemove events with a distance equal to zero.
* Updated the script to support Danbooru's changes to the image event listeners related to translation mode. When in translation mode, Danbooru's image event listeners will take effect. When viewing the image normally, the script will override all image click event listeners by capturing the event before it gets to the image and not allowing it to go any further. This may become necessary for other image mouse events in the future.
* Fixed textarea and text input use of the "n" key (translation mode toggle) on hidden posts