add banner tile that will replace image and link tiles (closes #218)
avoid TypeError when no styles defined on configlet
add functional tests for banner tile
refactor banner tile
deprecate image and link tiles
remove functional tests for deprecated image tile
add icon for banner tile
avoid failures because of test timeouts
Merge branch 'master' into banner-tile

Conflicts:
	src/collective/cover/static/tile-banner.png
Merge branch 'master' into banner-tile
Merge branch 'master' into banner-tile

Conflicts:
	docs/HISTORY.rst
Merge branch 'master' into banner-tile

Conflicts:
	docs/HISTORY.rst
Merge pull request #219 from collective/banner-tile

add banner tile that will replace image and link tiles (closes #218)