Fix import of csv files.

#6300 

This PR fixes the problems of import reported in https://github.com/openscholar/openscholar/issues/6300#issuecomment-48232442

The problem was using ``explode(",", $row)`` to get the row values. When the row includes commas this was not working.

After this fix import is working:
![selection_319](https://cloud.githubusercontent.com/assets/4497748/3505466/1a9fb298-065f-11e4-89ec-6c755b19057d.png)
![selection_320](https://cloud.githubusercontent.com/assets/4497748/3505465/1a9f9254-065f-11e4-98f7-43ae0623af8e.png)

For now marking this as a WIP since we still need to validate the "Path" value given.
- [x] validate the given "path" value.

Don't wrap with t. The entity validator will wrap the text for you.