Add support for flat horizontal list as category layout

This bug was fixed in the package unity8 - 8.00+14.10.20140814.1-0ubuntu1

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unity8 (8.00+14.10.20140814.1-0ubuntu1) utopic; urgency=low

  [ Michael Terry ]
  * Add --lightdm= argument to ./run.sh that lets developers choose
    which lightdm backend to use. Stop letting a user that is
    immediately denied via PAM into the shell by fixing some assumptions
    that a user which was not prompted was successfully authenticated.
    This is not a common situation, you'd have to manually change your
    PAM config. Fix a small console warning .
  * Make wrong-password handling much nicer by showing a pretty spinner
    while we wait for PAM, by improving the prompt text to match
    designs, by forcing the user to wait five seconds after every five
    failed attemps, and by supporting (but not yet enabling) an opt-in
    "factory-reset your phone after X failed attemps" feature.

  [ Michael Zanetti ]
  * bring back network caching in dash (LP: #1355729)

  [ Michał Sawicz ]
  * Add --lightdm= argument to ./run.sh that lets developers choose
    which lightdm backend to use. Stop letting a user that is
    immediately denied via PAM into the shell by fixing some assumptions
    that a user which was not prompted was successfully authenticated.
    This is not a common situation, you'd have to manually change your
    PAM config. Fix a small console warning .
  * Fix anchor in PreviewListView.qml.
  * Make wrong-password handling much nicer by showing a pretty spinner
    while we wait for PAM, by improving the prompt text to match
    designs, by forcing the user to wait five seconds after every five
    failed attemps, and by supporting (but not yet enabling) an opt-in
    "factory-reset your phone after X failed attemps" feature.
  * Add new horizontal list category layout. (LP: #1352226)
  * Fix qml tests - loader around PageHeader, more retries for selecting
    a scope and undefined attributes in mock overview scope.

  [ Leo Arias ]
  * Added autopilot helpers and tests for the launcher and dash icon.
  * Added an autopilot helper to click a scope item.
  * Added an autopilot test for focusing an app clicking the icon on the
    launcher.

  [ Mirco Müller ]
  * Allow ENTER/RETURN in a TextField to accept a snap-decision
    notification. (LP: #1305885)
 -- Ubuntu daily release <email address hidden> Thu, 14 Aug 2014 01:29:55 +0000

How can we test this layout?

It's already in use, for example in the music and weather scopes.