Issue 96 - Tile Mediacarousel enhancements

* Fix mediacarousel tile to hide items (layoutedit tab).
* Fix mediacarousel tile transiction beetween slides to grow or shrink
  tile as needed.
* Fix bin/instance to work again (z3c.unconfigure was missing).
* Fix package to make robotframework tests work.
* Added collective.cover testfixture profile to get basic data for tests.
* Created basic testfixture for brasil.gov.tiles to enable the tiles
  from this package be tested with robotframework.
* Created basic tests for mediacarousel tile.