Use generic JavaScript in MapReduce tests that will work even with server 2.2 (which uses a different JavaScript engine).
Removed SlidingTimeout.
added DropDatabaseAsync to MongoClient.
added DropCollectionAsync to IMongoDatabase.
added CreateCollectionAsync to IMongoDatabase.
added RenameCollectionAsync to IMongoDatabase.
added IMongoIndexManager and DropIndexAsync.
added GetIndexesAsync to IMongoIndexManager.
added CreateIndex operation.