CORE:  added imagex_page_slideshow

## Ready State: YES

This pull request adds an extension module, for field_splash which provides the ability to add media slideshow to pages.

## Requirements & Dependencies

* This new module requires 
https://github.com/imagex/imagex_splash_image

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

* This is not enabled by default in imagex_installkit, manually enable.
* Confirm field_splash is added to page CT, and that you are able to add media.