* Bump dependencies and add missing typing libraries
* Fix expose-loader breaking changes
* Expose jQuery using its own typings instead of ours
* Extend jQuery typings with our own custom $.fn helpers
* Use jQuery typings for Component's `this.$` attribute
* Format webpack config file
* Use Spin.js 3.1.0
We previously used the tobscure/m.attrs.bidi github repo, but that repo was recently taken offline. We decided to integrate it as a util instead of publishing it as a separate package since we seem to be the only project using it, and adopting it into a new project requires barneycarroll/mattr, which does not seem to be used anywhere.
The code added here was taken from https://github.com/askvortsov1/m.attrs.bidi, a fork (without changes) of the tobscure repo. Support for alternative module systems and ways of registering bidi were removed, and the file was formatted in compliance with our prettier config.
* Run extenders exported by extensions
* Add some basic extenders
* Patch Mithril as the very first thing so extension code can run safely
* Load the payload into the app before booting extensions
* Setup default routes before booting extensions
* Replace gulp with webpack and npm scripts for JS compilation
* Set up Travis CI to commit compiled JS
* Restructure `js` directory; only one instance of npm, forum/admin are "submodules"
* Refactor JS initializers into Application subclasses
* Maintain partial compatibility API (importing from absolute paths) for extensions
* Remove minification responsibility from PHP asset compiler
* Restructure `less` directory
