Removed legacy display types.
  AddThis module contained some small non generic display types. They where
  removed in favor of the display types added in the addthis_displays submodule.

Redesigned the config page.
  The settings page has been made more condensed and options have been merged
  into clear categories. There are some options that where removed because of
  legacy functionality that is now support inside the display types.

There was a bug introduced when adding the different displays through formatters
this bug was not noticed but reported by vasike in issue #1308970.

The markup is now create through a seperate hook function. This is more
dynamic and creates the possiblity to add the theme function better.

Todo: we need to test settings for a formatter and add a field instance to
the block. Settings need to be generic and also be able to be set on the
theme function.