* Relocate chart type and dataset type defaults
* Update types
* Separate overrides and descriptors
* Update derived sample, use merge for inherit
* Don't merge overrides
* Review update
`controllers.*.js` and `core.datasetController.js` are now importable (no more function export), that's why there is so many changes mainly due to one indentation level removed. Split code for `bar/horizontalBar` and `doughnut/pie` in separate files, added a global controllers import (`src/controllers/index.js`) and add tests to check that all dataset controllers are correctly registered under `chart.controllers.{type}`.