DAR-2366

**DO NOT MERGE!!!**
BadBoys will code review it and QA before merging to `dev`.

* added new getter into `wikia.fluidlayout` module (`getRightRailWidth()`),
* added new getter into `wikia.preview` module (`getPreviewTypes()`),
* passed `isWidePage` parameter from `PageControls.js` to `wikia.preview` modal and changed the logic depending on that flag.