Adding configuration form for Display Types to the AddThis Block

There are already two issues about not having the format settings for the AddThis Display type in the block. The current implementation is only the default settings, but the form for Field Formatter settings in the Manage Display page is added through ajax.

One option to alter the current display is described here and is done through a alter implementation. But it would be better to implement the same form for settings as on the Field Formatter settings.

This issue is created as reference to look at how to implement this for blocks.

The two issues I mentioned:
#1364822: Add help pointer to enable AddThis Displays with basic display types implementation
#1363682: Display Type in Addthis block