Also created a contributing/coding_conventions landing page separately from the PHP ones, since we now need to account for JS and CSS conventions as well
* More pointers to new build tooling docs in upgrading guide
* Fixed docs references to moved files
We don't want to mandate every module to switch from javascript/ to client/src,
but at the same time shouldn't reference non-existant files and confuse newcomers that way.
* More pointers to new React docs
- Removes thirdparty dependency History.js
- Adds thirdparty dependency Page.js to manage client-side routing
- Adds a wrapper around Page.js for SilverStripe specific behaviour
- Increased minimum browser requirement to IE10. Native HTML History API routing requires IE10 or newer (necessitated by removal of History.js)
- PJAX pannel loading via now uses promises rather than callbacks
- Adds getClientConfig method to LeftAndMain which can be used to pass config from to the front-end client
