This migrates over the required English translations under their
new names.
The "Searching" message has also been adjusted to use "Searching..."
instead of "Loading more results...", which is what it used to
say sometimes.
This also changes the AJAX handler to call `abort` when needed.
This adds a custom r.js build for i18n, which processes each JS
file in the `select2/i18n` directory and builds it.
So far only the "No results found" translation has been added.
