Reading/Web/2015 Q1 Feature stabilization

As part of work on 2014-2015 Q4 and 2015-2016 Q1 the Reading Web team has been stabilizing features on MobileFrontend, clearing out the ones that didn't make sense and promoting to beta or stable the ones that made sense.

Here's a list of the work involved, see the phab tasks for the status of it.

Removing features

 * Wikidata infobox on MobileFrontend's alpha (phab).
 * Read in another project on MobileFrontend's alpha (phab)
 * Experimental search header on MobileFrontend's alpha & beta (phab)

Features from Alpha to Beta

 * Font size changer (phab)
 * Mobile image gallery (phab)
 * Mobile categories interface (phab)
 * Link preview (phab)
 * Commons category media viewer (phab)
 * Wikidata description at article start (phab)
 * Report an error (phab)