aloha 8.x-2.0-alpha3

For alpha 3 of Spark for Drupal 8.

Changes since 8.x-2.0-alpha2 (9 commits):

• #1811346 by Bojhan: Added Lessen gradient.
• Refactor and improve testability of aloha_add_format_settings().
• WYSIWYG in core: round one — filter typeshttp://drupal.org/node/1782838 got committed, woohoo!
• As of the previous commit (for issue #1815246), you now need to apply a different core patch.
• #1815246 by Wim Leers: Stop relying on filter_get_allowed_tags_by_format(), figure out which tags & attributes are allowed through blackbox testing.
• #1782372: Initial, rough support for the Image plug-in. Comes with searching all images on the site.
• Updated Aloha Editor build to a post-0.22.2, pre-0.22.3 build, including my latest Image plug-in bugfixes that were merged.
• Fixed #1813288 by Tobias Steiner: drupalcontenthandler.js uses Sanitize incorrectly
• Shell script to facilitate Drupal 8 patch testing.