Revert changes to viewExtent. Move check for zero vector sooner and adjust if needed.
Update CHANGES.md.
Merge branch 'master' into viewExtent

Conflicts:
	CHANGES.md
Merge branch 'master' into viewExtent

Conflicts:
	CHANGES.md
Add a couple more viewExtent tests.
Merge pull request #1433 from AnalyticalGraphicsInc/viewExtent

Fix view extent