Easy JSHint cleanup

Did a pass of all of our javascript with JSHint, and cleaned up missing semicolons and strict equality suggestions it pointed out.

I did not deal with any other issues, of which there were many, and I didn't touch any of the `tiny_mce` javascript because we didn't write it. 
Hmm... according to docs, `HTMLInputElement.value` is always a string. This code has a note about an IE-specific fix to prevent `null` casting to a string. Needs to be tested in IE7/8.