Support legacy change details

Add support for using the legacy method of getting
 change details from the 'query changes' endpoint.
Merge StaticWebAddress into GerritURL
GerritURL: Self-manage gerrit base URL
Add new legacy commit details processor
Note: With this commit, change details for Omni
 are now supported.

Change-Id: I28f3c7d024c13d90836627799dca1507e21ab800