Reach Editor parity with Ember

closes #2426, closes #2781, closes #2913

**Some issues:**

* I didn't try to port `mobileCodeMirror.js` .. I think mobile is a different beast and I'm not comfy there yet. Also I'm not sure what our strategy is for that with Ember.
* I didn't understand what was going on with [`fileStorage` in uploadManager.js:137](https://github.com/TryGhost/Ghost/blob/master/core/clientold/assets/lib/editor/uploadManager.js#L137) so I did [gh-markdown.js:25](https://github.com/appleYaks/Ghost/commit/aa1196611882322b7fceb26cc0ccb1b579e01535#diff-1cd2ff4e951d1133c34d516ff81b2182R25) and set it to `false`.

I did a lot of testing, but I ain't no superman. More heads are better than one, so please let me know where the bugs are at, or how to reproduce them.