Blocked on: T158980
After having experimented with using a bundler in Page previews, We will use webpack to generate MobileFrontend's mobile.startup module.
This will
* reduce size of RL module
* Avoid unnecessary file loading in ResourceLoader
* Make it easier for us to port to a submodule in future if necessary
* Remove the need for unnecessary globals
* Use npm libraries
* Allow us to experiment/investigate using Es5/6, template compiling
= acceptance criteria
[] Add a build_resources folder
[] Use webpack or another tool to generate a single JS file that is included by mobile.startup that includes all the existing JavaScript
[] Templates and LESS files will continue to be loaded via ResourceLoader
[] Use commonjs where possible for exporting/importing
[] There is fast isolated unit testing with npm run test:unit e.g. https://gerrit.wikimedia.org/r/#/c/282899/
[] Integrate code coverage reports and fail job on coverage decrease
[] The closures around every file should be unnecessary after these changes (RL wraps code so no global var leakages, and eslint protects against unused/undefined variables used)
e.g. we can remove the following pattern
```
( function ( M, $ ) {
```