Always on banner on special, add a welcome message to the landing page

Thes message is a placeholder that can be easily customized
using wikipedia's MediaWiki namespace messages, or for defaults
on all language sites - in translatewiki. The message will be
parsed as blockparse.

The banner will always be shown on the special page per biz request

The gray blank header at the top is also now hidden via in-code CSS
until mobile designs a way to hide it via some setting.

Removed .mw-mf-banner.mw-mf-banner-undismissable class -- very strange
usage, possibly due to legacy code. Might have to re-add it later if
a bug of some sort surfaces. Removed associated js code.

Change-Id: I944eec59eaf6e83a9828cb284fe8d21274e7151b
Merge "Always on banner on special, add a welcome message to the landing page"