Feature: LDC-250 - finalist & winners notifications

## Ready State: Yes

This pull request is related to the following JIRA tickets: 
https://imagex.atlassian.net/browse/LDC-250

## Requirements & Dependencies

None

## Deployment Instructions

* Merge code.
* Enable imagex_contest & imagex_contest_permissions & imagex_contest_addthis
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Ensure the email address of the user you're logged in as matches your own 
* Create a contest node and then add at least 1 contest entry for that contest.
* For the given contest, click the "Contest Overview" tab and use bulk operations to trigger the "Select As Finalist" & "Select As Winner" operations. Ensure:
  * Step 1 displays the option to notify or not notify the entry author via email
  * Yes option is default
  * Selecting yes, you receive an email
  * Selecting no, you do not receive an email