MISC: File field fix.  tags  field replaces topics

## Ready State: (yes)
Ready : Yes

This pull request replaces:
*https://github.com/imagex/imagex_blog/pull/1#issuecomment-25027539

## Requirements & Dependencies
imagex_common_fields

## Deployment Instructions

* Merge code.

## Usage/Test Instructions

Enable Blog, ensure content type is correct and file_field exists