Suggestion / Add the possibility to search on a field and suggest on another

Add the possibility to have a search field on a specific lucene field and the suggestion list based on another field. The main idea is to restrict the list of possibilities for a full text field which will suggest numbers, uuids, filepath fragments, ... which could be complex to understand for the end-user. For example:

![image](https://cloud.githubusercontent.com/assets/1701393/3030335/c901ff12-e03f-11e3-9c97-553803c66100.png)



In that case, a new field named anylight is created only indexing title, abstracts, keywords from which the suggestion will come from for the full text search field.