Expand all Text for Checking Hidden Categories

An example of this issue is [1] which has a template that actually adds the
_HIDDEN_ keyword. The other change proposed here is not to use regular
expressions for that match, it is pointless.

We still search for the _HIDDEN_ keyword because newly created empty
categories do not show up in the category table, and thus are not
returned by the API (bug #48824)

[1] http://commons.wikimedia.org/wiki/Category:Cultural_heritage_monuments_in_Panama_with_known_IDs

Change-Id: I4d1acce3c3c311724a577435829630c8e2548581
Merge "Expand all Text for Checking Hidden Categories"