CON-1797 + CON-2104 | Content Recommendations for Venus + Recommendations API

https://wikia-inc.atlassian.net/browse/CON-1797
https://wikia-inc.atlassian.net/browse/CON-2104

Recommendations API:
* ```getForArticle``` - serves recommendations for article from different data sources:
** Category based recommendations - old read more
** Video recommendations - must watch videos module
** Cross wiki article recommendations by hub + language

```nodeFinder.js``` taken from CON-1784, it'll be unit tested there.

```venus.layout``` from now can calculate grid column width on all verticals + has more info connected to layout

Small changes on Recommendation layout + recommendations tracking

Don't merge without https://github.com/Wikia/config/pull/747
Q: Why we need to prefix all js files with extension name?