The actual change is in src/mongo/shell/collection.js with the remaining changes
to adjust tests to the new api.
The "ideal" arguments are now an array of pipeline ops and an optional object
with extra top-level options for the command (such as {explain: true}. For
backwards compatibility, we still support the varargs style where each argument
is a pipeline stage, but there is no way to specify extra parameters in this
mode.
Date - Date : NumberLong(Milliseconds between times)
Num - Date : Error
Date - Num : Date(original - Num as milliseconds)
Date + Date : Error
Num + Date : Date(with num treated as millis)
Date + Num : Same as Num+Date
