R1:b592630d7259

Provide more structure to PHUIObjectBoxView

Summary:
Three changes here.

- Add `setActionList()`, and use that to set the action list.
- Add `setPropertyList()`, and use that to set the property list.

These will let us add some apropriate CSS so we can fix the border issue, and get rid of a bunch of goofy `.x + .y` selectors.

- Replace `addContent()` with `appendChild()`.

This is just a consistency thing; `AphrontView` already provides `appendChild()`, and `addContent()` did the same thing.