Stop using "Object" in annotations

[joeyparrish]

There are several reasons we have used the "Object" type in our annotations in the past:

1. For an open-ended type, such as in configure()
2. As a Map or Set, since we didn't always have ES6 Maps & Sets available to us
3. Because we didn't want to bother defining a type

Reason 1 may have to stick around. I'm not sure yet.

Reason 2 is no longer valid, and these should be converted to Maps or Sets.

Reason 3 was never valid, and this especially needs to be fixed.