Additional MongoDB adapter improvements
 * suggest mongofill/mongofill
 * Instantiate MongoCollection in MongoDBResourceManager
 * Allow for all Mongo/MongoClient options to be passed to constructor
 * Implement flushable interface
 * Index collection on 'key' when created
Cleanup use statements/remove array short syntax
Merge pull request #2 from protecinnovations/feature/mongodb-caching-improvements

Additional MongoDB adapter improvements