Bug 44133: Deprecate mwMobileFrontendConfig and setConfig, getConfig

use mediawiki core equivalents
add new config variables where missing

On dynamic page loads for time being update certain config
variables (in future a current page object might be used instead)

document and tweak getArticleUrl and use it where necessary rather
than resorting to config variables

Change-Id: I5b2b58140d46bd1f2e0407328b8bab8bce4d1680