Edit section and subsection at course outline page.

WIP.
I'd suggest to rewrite it so:
```javascript
conversions: {
  release_date: 'start',
  due_date: 'due'
},
preprocessFieldNames: function(metadata) {
  var result = {};

  _.each(metadata, function (value, fieldName) {
    if (_.has(this.conversions, fieldName)) {
      result[this.conversions.fieldName] = value;
    } else {
      result[fieldName] = value;
    }
  }, this);

  return result;
}
```
And do not forget about docstrings.