Admin should only edit their own organization's measurements

[CraigJZ]

Admin for an organization should only be able to edit their own organization's measurements. Currently, an admin can edit all organizations' measurements. This will be partially handled by #1028 but we should also limit authorization for these actions programatically.

Criteria for completion

• Restrict editing measurements to the organization level. Editing is already limited to admin users. Those admin should only be able to edit their own organization's measurements.
• Add specs to exercise this new behavior.