Feature:  RSS Widget, Added Feed Image and Option to Toggle off Descripton

This Pull Request Adds two fields to the RSS widget

1) field_image
which allows an image to be associated with a feed

2) field_exclude_description
a checkbox, which when checked omits the description printout for a given RSS feed block.  

Updates for printout have been added to the template, which checks to see if these values are set and acts accordingly.

 ##Ready State: Yes

## Requirements & Dependencies
imagex_widgets

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

* Confirm after install/build that two new fields exist.
* Confirm that images is printed out when exists
* Confirm alt tag text is correctly added - or the default.
* Confirm that for widgets without these set, everything continues to work as expected