First pass for content resubmission

This first approach avoids tampering with the validation in the submission model 
```
  validates_uniqueness_of :content_id, :scope => :feed_id  #Enforce content can only be submitted to a feed once
```

The downside to this approach is that the user's submission history does not reflect re-submissions. Only one submission will show up instead of one for each re-submission. 

#1079