Feature: Added message & message_ui modules needed for LDC-246

## Ready State: Yes|No

This pull request is related to the following JIRA tickets: https://imagex.atlassian.net/browse/LDC-246

## Requirements & Dependencies

None

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

Run the imagex_installkit drupal-org.make file and ensure the message & message_ui modules are downloaded to /profiles/imagex_installkit/modules/contrib directory.

#### Notes

I've added the 2 modules as dependencies in imagex_installkit.info but seems a bit overkill as they'll be dependencies (& in the make file) the the imagex_user_activity feature. Let me know if you want me to revert this.