Feature: Add old to XML format converter to the browser compiler

Feature/Parity: `dialog:user-input` default value argument

Bugfix/Infrastructure: Bump NetLogo for manual extension loading

Bundled extensions weren't correctly getting picked up for forced
installation.

Parity: Support `__clear-all-and-reset-ticks` legacy prim

We don't force people to remove it, so adding it here.  Maybe a better
way is to warn users in the front end, or just auto-replace it, but this
works for now.

Tests: Add CoffeeScript linter to quick test script

Bugfix/Parity: Remove incorrect workaround for String ext prim

After looking at the workaround, it was not correct.  In thinking more,
the default behavior on JavaScript split is what we want, so I updated
desktop to use that instead.  Updated tests to match what desktop does
now.

API/I18N: Add a method to check support for a locale

Bugfix/Refactor: Switch to stand-alone image import for Bitmap

Bugfix: No extra args on concise variadic prims with `reduce`

Infrastructure: Bump Scala.js to 1.10.1