Previous translations moved to source

I moved all of my translations from the main enchant.js file to the
source files.

I also cleaned up my work in a couple of places. In general, I've been
cleaning up little things like encasing parameter names in [] for
@param lines. Specific changes are listed below.

Core.js -- I finished going through its docs.
Event.js -- There were a lot of little things which were grammatically
correct and matched the wording of the Japanese documentation but which
didn't follow standard practices for programming documentation in
English. I cleaned that up.
EventTarget.js -- Added Japanese for EventTarget.on().

Concerns:

Core.js
- Lines 246 and 249 in my commit -- Should the documentation say
game.start() or Core.start()?
- Lines 926 and 951 in my commit -- Should these really be the same?
And should they really link to Core.start() instead of Core.resume()?