The SoftwareUpdate Plugin had a bug that caused way too much check data to be stored in the configuration, leading to plugins potentially being stuck in an "update available" loop although the update had already been applied. Now only the current version of github_commit update types is persisted, not the full check configuration.
Also introduced a configuration version and made the migration function migrate old configs to remove anything that was same as the default supplied for the "octoprint" and all plugin hook checks. That should clean things up in existing installations.
When any plugins are enabled/disabled, the client now gets a trigger to fetch a fresh list of update information from the server. This should take care of any old popups still hinting at now uninstalled plugins.
If plugins get enabled or disabled, the update check configuration needs to be refetched next time it's needed since there might have been changes to plugin implementing the check_info hook.
