Self-hosted extensions that update aren't appearing in Changelogger

[keithx2]

If an extensions updateUrl is not undefined, then it is self-hosted. Changelogger is not logging these extensions when they update when 'Should updates with no changelogs be ignored' set to false. A link to the homepageUrl (if it exists) could be used by Changelogger instead of an AMO link, with the updateUrl as a fallback.