Within the flow of HttpFetchException, the actual exception from curl is preserved and logged. Make HttpFetchException a pretty exception for when it is shown to users.
- Reduced options to single new configuration paramter instead of two.
- Moved more logic into UserAvatars class.
- Updated LDAP avatar import to also run on login when no image is
currently set.
- Added thumbnail fetching to search requests.
- Added testing to cover.
Related to PR #2320, and issue #1161