Switch parsing function name to be like ElementTree

(cherry picked from commit 85183bbd8279fe44ff5755ec3602631dfe04230b)

Conflicts:
	python/Objects.py
	python/make_differential_dfxml.py
	python/summarize_differential_dfxml.py
	python/test_Objects/try_verifying_image_sha1s.py

Conflicts were mostly documentation.  The summarize script had a few
variable definitions to update; no program-logic changes occurred.