Update documentation to reflect ordering changes

To bring woCompare functionality in line with KeyString total ordering, Dates and Timestamps are now disentangled in sort ordering, with all Dates occurring before all Timestamps.

1) http://docs.mongodb.org/manual/reference/bson-types/ should be updated with the new ordering. (Item 10. under Comparison/Sort Order)
2) Compatibility notes should call out (Important or Warning) that any use of timestamp to store datetimes is incorrect, and the two will not be interoperable in terms of comparison as of 2.8. Unfortunately, the .NET and Node documentation don't correctly proscribe use of Timestamp. Should also note for third-party administrative tools that may examine the oplog that the comparisons now operate differently.
3) Any appropriate occurrences in the aggregation documentation should include a versionchanged and note with behavior change. I have not found any but YMMV.

See linked.