Async Index Operations

Added an executeAsync to the CreateIndexes, DropIndexes and GetIndexes operations
Added executeAsync to User based operations

Added abstract base BaseUserOperation class
Updated CreateUserOperation
Updated DropUserOperation
Updated UpdateUserOperation
Updated UserExistsOperation
Added GetCollectionNamesOperation
Transform block for user operations
Added executeAsync to FindAndRemoveOperation
Added executeAsync to FindAndReplaceOperation
Added executeAsync to FindAndUpdateOperation