Support for multiple fields with the same name

[Shazwazza]

Currently if you use DocumentWriting event and create multiple fields with the same name, it will index just fine since Lucene supports that. However, when you search you will get a dictionary error because it is trying to add the same field to the dictionary multiple times.

Since we cannot change the dictionary result since that is a breaking change, we'll support this by doing the following:

The normal dictionary of values will contain the first value, however the there's a new method on the SearchResult object: public IEnumerable<string> GetValues(string key) which will give you all of the values indexed for that field. This method will never return null, if a key doesn't exist at all an empty collection is returned.