CSHARP-797: Strengthen unit tests (work in progress).
CSHARP-797: More unit tests.
CSHARP-797: Changes in response to code review comments and getting tests to pass against server 2.4.
CSHARP-924: Add IsModifiedCountAvailable and change ModifiedCount to throw when modified count is not available.
CSHARP-924: Use nullable long for ModifiedCount internally.
CSHARP-797: Add more unit tests.
CSHARP-797: Add unit test for w > 1 against standalone server.
CSHARP-797: Add unit test for { j : 1 } when server is run with --nojournal.
CSHARP-797: In BulkWriteOperationTests instead of using RequestStart assume that the cluster is homogenous and that whatever features the primary supports are also supported by all other members.
CSHARP-797: Always drop the collection at the beginning of the test. Removed some unused temporary variables.