We now use /usr/local/opnsense/version/xxx as our version database.
Apart from the core package, opnsense-update(8) also puts its own
version information in there. To stay somewhat consistent, the
version file should resemble the package name, even though that
looks strange in our case: /usr/local/opnsense/version/opnsense.
It's just that /usr/local/etc is too open and might clash with
other things in the future.
* Add pkg autoremove for stale package removal.
* Refactor progress file output in case it'll change.
* Truncate the progress file directly on startup.
Unfortunately, that doesn't solve the lingering of upgrade
info after navigating away from the firmware page. Need to
find a better solution here...
PHP plugins may change and then clobber the custom php.ini we have
previously generated. To make sure everything keeps running smoothly,
always regerate it directly after an upgrade, even though there may
have been no changes.
