Fixed two blocker issues that kept the OpLog util from functioning

1) The pattern match on input wasn't looking at the typeCode field, so all matches failed.
2) It turns out that Master/Slave does *not* include an OpID; therefore, made it Option.

It's hard to rig a test for this as it requires a lot of functional
interactions and a local replica set / master slave. Manually verified &
test forthcoming.

TODO: Subtypes of OpLogEntry for RS vs. Master/Slave?