CSHARP-1041: Moved most exceptions into Core to make backwards compatibility easier.
CSHARP-875: Removed all code from high level driver that now belongs in Core and temporarily replaced it with NotImplementedExceptions.
Got enough of the legacy API working on top of Core for the test configuration to startup and for the first test (TestMetaText) to pass.
Ported the classes that emulate CRUD opcodes using write commands from 1.x to 2.x.
Removed everything but Version from MongoServerBuildInfo.
Move IsWritable to an extension method on ServerType in Core.