Make zerodot landing page fast and have search.

* On a 2G connection, the landing page or Main Page takes something
  like 45 seconds.
* Let's see if we can get that down to 5 seconds or less by making
  it a self-contained page with minimal stuff.
* To help users who have an idea of what they're looking for,
  let's offer a simple search form for fulltext results, too.
* On this new zerodot landing page we sacrifice suggest-style
  searching. Many devices on zerodot lack rich JavaScript support.
* But the search field does employ fulltext search, which is
  probably more natural.
* In a future state, we could consider a lightweight suggest-style
  search, perhaps, but it would need to be really lightweight.
* Because the article viewing experience has a language picker and
  only select languages are popular in practice anyway, we don't
  bother with the full language picker anymore - it takes a lot of
  extra bytes. We only show the select languages popular on a given
  operator's network for the landing page.
* In the future, let's consider bringing this to the mdot landing
  page as well.
* It's unclear whether this should replace the Wikipedia Zero
  auto redirects for the case when there's only one language defined
  for the operator and the user is sent to that language's Main Page
  automatically. But it's worth consideration. We want users to get
  access to both the Main Page and to search.
* Furthermore, would it make sense to have a link to Random on this
  page? This could be a really exciting feature for people who may not
  otherwise discover it on the sidebar (for whatever reason).

Change-Id: Ia676a3ea5f262f0a60890e8daefd1905a0b57843
Merge "Make zerodot landing page fast and have search."