Metadata: Read Zulu/UTC dates from Exiftool JSON

[graciousgrey]

Acceptance Criteria:

• Read zulu/utc dates from exiftool json
• Write unit test

[lastzero]

Expected date/time format changed from 2006:01:02 15:04:05-07:00 to 2006:01:02 15:04:05Z07:00. Now successfully parses 2006:01:02 15:04:05Z in addition to numeric time offsets.