Promote the UbuntuWebView as an official API

A significant number of webapps use the UbuntuWebView component already, so we will definitely need to maintain the old naming.

> Note we should not use simply WebView as that will collide with
> the webkit version.

Actually, it’s probably fine to simply use WebView, as QML supports qualified module imports that allow doing:

  import QtWebKit 3.1 as WebKit
  import Ubuntu.Web 0.2 as Ubuntu

  WebKit.WebView {}
  Ubuntu.WebView {}

This bug was fixed in the package webbrowser-app - 0.23+14.10.20140609-0ubuntu1

---------------
webbrowser-app (0.23+14.10.20140609-0ubuntu1) utopic; urgency=low

  [ Ubuntu daily release ]
  * New rebuild forced

  [ Olivier Tilloy ]
  * Move version 0.2 of the API to "Ubuntu.Web" namespace, rename
    "UbuntuWebView" to "WebView", and document the public API intended
    for application developers. The legacy namespace and component name
    are kept around for compatibility with existing applications.
    Version 0.1 of the API remains untouched (it is deprecated).
    Packaging changes: - new qtdeclarative5-ubuntu-web-plugin package
    that contains the new namespace and name for the public QML API -
    updated runtime dependencies for webbrowser-app, webapp-container
    and qtdeclarative5-ubuntu-ui-extras-browser-plugin - updated
    descriptions for all packages - added missing multiarch stanza for
    webapp-container-autopilot - added missing predepends stanzas for
    multiarch packages (LP: #1324180)
 -- Ubuntu daily release <email address hidden> Mon, 09 Jun 2014 10:44:31 +0000

Almost done, what remains to be done is polish the documentation and publish it on developer.ubuntu.com.

Moving back to "in progress" as the documentation is not publicly available yet.

Documentation is now available online at http://developer.ubuntu.com/api/qml/sdk-14.10/Ubuntu.Web/.