Alternate image swapping + Adjust search width

* Allows the search listing to expand and try to fill the user's screen and, if they should change the window, readjust to the new dimensions.
* Allows the user to make clicking the image swap between the original and sample images.
* Allows the user to make arrow keys navigate pages again.
* Removed disabling arrow nav on posts sine Danbooru doesn't use the arrow keys now.
* Removed the old arrow nav for the time being.
* Misc tweaks/fixes.

Should take care of issues #7, #8, and #9.