Remove unneeded auth classes. Fix BuildingSync and HPXML API endpoints

[nllong]

Any background context you want to provide?

BuildingSync and HPXML were displaying quantities in the elements.

What's this PR do?

Cast the Quantity fields to their magnitudes before persisting to the XML's (BuildingSync and HPXML).

How should this be manually tested?

Unit tests were added.

Go to the following endpoints via the API:

• /api/v2.1/properties/234/building_sync/?cycle_id=x
• /api/v2.1/properties/234/hpxml/?cycle_id=x

What are the relevant tickets?

N/A

Screenshots (if appropriate)

Definition of Done:

• Is there appropriate test coverage? (e.g. ChefSpec, Mocha/Chai, Python, etc.)
• Does this PR require a Selenium test? (e.g. Browser-specific bugs or complicated UI bugs)
• Does this PR require a regression test? All fixes require a regression test.
• Does this add new dependencies? If so, does PIP, npm, bower requirements need to be updated?