Implement OS specific information discovery (#11446)

* Implement OS specific information discovery
That way it doesn't have to be fetched during polling
Also improve discovery process, os is only detected once, in the core module.
EXA is the test os, a couple improvements there.

* Use local variable, then unset it so we don't pollute.

* fix style issues

* test and other fixes

* attribute update fixes

* Update exa data, need new source data

* null missing "os" values

* fix ftos odd character

* fix ftos odd character

* only null for new style or we will reset to null every discovery

* Move device observer to own class

* Handle location, relocate event logging

* update exa e7-2 data

* update ird test data, apparently unicode is now working.

* update Linux ntc, now uses correct icon

* Only load all os on the web, also, we can't load existing the the database isn't connected.

* only for devices that have a location

* revert ftos test data apparently

* revert ird

LibreNMS/Interfaces/Polling/OSPolling.php

@@ -0,0 +1,35 @@
+<?php
+/**
+ * OSPolling.php
+ *
+ * Custom OS polling data, this could be anything including custom graphs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @package    LibreNMS
+ * @link       http://librenms.org
+ * @copyright  2020 Tony Murray
+ * @author     Tony Murray <murraytony@gmail.com>
+ */
+
+namespace LibreNMS\Interfaces\Polling;
+
+interface OSPolling
+{
+    /**
+     * Poll additional OS data.
+     * Data must be manually saved within this method.
+     */
+    public function pollOS();
+}