Hotfix: added addthis_displays module as dependency since nothing works ...

## Ready State: Yes

Found when doing AddThis functionality for the contest feature, relates to all addThis features.
Without addthis_displays module enabled the addThis field is disabled and not useable (not sure how it was developed without it).

## Requirements & Dependencies

None

## Deployment Instructions

* Merge code.
* Enable module imagex_addthis & imagex_page_addthis
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Go to /admin/structure/types/manage/page/display and ensure the "AddThis" field format now has "Basic Toolbox" & "Basic Button" options