Implementation of DictionaryIndexer

Hey Mike, here is the DictionaryIndexer. I think Daniela already sent you the QuerySuggestionsIndexer too. They both follow a similar structure with a couple of differences especially for the nGrams (QuerySuggestions only have start.. nGrams). The CustomEntries interface is designed to contain everything about general scopes. This is necessary for QuerySuggester in order to create the filterQueries.