VHS recorder: Fix src warnings in lift-mongodb and lift-mongodb-record

lift-record and lift-mongodb-record should be done here for src stuff, contributing towards #1534.

@eltimn it would be handy if you could have a look here—I addressed some mongo-related
deprecation warnings, specifically related to using `Mongo` vs `MongoClient` and `MongoOptions`
vs `MongoClientOptions`. I dealt with it pretty quick-and-dirty, but I realize amongst other things
`MongoOptions` defaults write concerns to a different value than `MongoOptions`. I imagine we'll
want to deprecate the `MongoOptions` constructor in 2.6 and provide an overload that takes
`MongoClientOptions`?