Improve handling of folder syncing errors

[jkemp101]

Folders may fail to sync due to transient or permanent errors (e.g. access denied). Errors with one or more folders should not stop syncing the remaining folders. After sustained errors the folder syncing should be paused or skipped during an initial sync. These errored folders should then be checked periodically (e.g. once a day) to see if syncing is now possible.

[jkemp101]

If this issue is stopping an initial sync you can manually skip folders by marking them like this:
update imapfoldersyncstatus set state='finish' where id = 1234 and account_id=6578