Add "nupdated" field to SystemProfileInfo class.

The field "nupdated" that shows the number of documents updated by an update operation was missing from the SystemProfileInfo class. It is now added as a .NumberUpdated property.
CSHARP-632: correct over-generalization of convert expression removal.
added in Tim Kellogg's tests for ordering by value types.
addressed code review comments.
added Einar to contributor list.
Remove MongoUrlBuilder ResetValues and move the initialization code to the no-argument constructor.
CSHARP-567: removed Value property from BsonDateTime.

Conflicts:
	MongoDB.Bson/ObjectModel/BsonDateTime.cs
CSHARP-562: Deprecate ReadFrom/WriteTo in the BsonDocument object model.
CSHARP-645: Replace AsDateTime with ToLocalTime and ToUniversalTime in BsonValue (and related changes).
CSHARP-562: Change GetDocumentId in BsonDocumentSerializer to always return an instance of BsonValue.
Merge branch 'csharp562v18'
Correctly serialize lock statistics in system.profile.

Problems:

 1. The SystemProfileInfoSerializer used the name "lockStatMillis" for the lock statistics key name. At least in MongoDB 2.2 the correct name is "lockStats"

 2. The SystemProfileLockStatisticsSerializer used the names "timeAcquiring" and "timeLocked" where the right names are "timeAcquiringMicros" and "timeLockedMicros".

 3. The timespan units used were milliseconds, where the correct units are microseconds. Added the option MicroSeconds to the TimeSpanSerializer and set the SystemProfileReadWriteLockStatisticsSerializer to use Microseconds.

 4. NOT FIXED: The TimeSpanUnits.Nanoseconds is wrong. 1 millisecond is not 1000 nanoseconds, its 1000000 nanoseconds. This option should probably be removed since TimeSpan doesn't have nanosecond precision (most accurate precision is ticks, where 10000 ticks are one millisecond).
CSHARP-647: Improvements to TimeSpanUnits and TimeSpanSerializer.
CSHARP-589: isolating the core from the public api.
CSHARP-649: MaxConnectionLifeTime and MaxConnectionIdleTime are now strictly enforced.
CSHARP-603: initial commit for SASL authentication.
CSHARP-603: refactoring.  Full support for SecureString.
CSHARP-603: added support for setting credentials via url.
cleaning up warnings.
CSHARP-603: Reverted commits 6f33dd through 95cba9. They were pushed by accident before the work was completed.