Cleaner tryNext() implementation for MongoCursors

JAVA-1326
Fix DBCursor#tryNext support for curr() and numSeen()

Missed in JAVA-1255
Added support for authMechanismProperties on the connection string

JAVA-1466
Fix checkstyle nit
The MongoTimeoutException thrown from BaseCluster methods now includes a short description of the cluster state,
which includes a short description of each server being monitored, which includes a short description of any exception
thrown while monitoring.

JAVA-1477
Removed duplicate ShutdownHook in rx test fixture.
JAVA-1486 fix max/minkey typo and binary encoding and decoding test
 Fixed a few stray Javadoc issues in the driver-core module, so now enabling the Checkstyle rule for it
Removed spurious comment in checkstyle.xml
Clarified in Javadoc that $snapshot only prevents duplicates.

JAVA-1408
Removed unused non-public field/methods in DBCollection

JAVA-1430