Add API documentation to documentation build, turn off documentation warning check

[edwardhartnett]

DESCRIPTION OF CHANGES:

In this PR I add the generation of the API documentation to the documentation build.

This generates some warnings I can't handle yet, so I also turn off warning checking (for now).

TESTS CONDUCTED:

N/A

Machines/Platforms:

N/A

Test cases:

N/A

ISSUE:

Part of #502