* Updating client dependancies. Switching to using yarn.
* Updating React
* Moving pure components to using function syntax (performance gains with newer react version)
* Updating client dependancies.
* Ignore .yarninstall
* Enabling pre-lockfile because it's the entire point of using yarn.
* Removing old webpack config
* Moving to new prop-types
* Fixing ESLint Errors
* Updating jest snapshots.
* Cleaning up package.json
* Update error page to use Markdown and add error for missing OAuth code
* Add line breaks to error messages
This is to make the error message easier to read.
* Update en.json
