CORE: Add radioactivity

## Ready State: Yes

This pull request is not related to any tickets, but is as a result of trying to do a build for PLNU with content types: blog, events, news and page - and getting dependency error for radioactivity.  As discussed in Skype adding this to core makes sense given the dependencies of most CT and other features (like Q&A)

## Requirements & Dependencies

* imagex_radioactivity
* Radioactivity Module

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

* Ensure radioactivity is downloaded as part of build process
* Ensure radioactivity is enabled as part of install process
* Ensure imagex_radioactivity feature is enabled as part of install process
* Ensure for CT with this dependency they are assigned a radioactivity decay profile.