* Ping only device doesn't display
if os was set to something, ping os wasn't loaded and we try to get overview graphs from it.
* Fix snmp_disable device page load error
When other os is set.
* Revamp os setting loading
the only safe way to access is Config::getOsSetting()
* Remove getOsSetting fallback behavior
Most instances don't use it and it can have unexpected results Config::getOsSetting('blah', 'group') == 'librenms'
* refactor and remove unneeded load_os/loadOs calls now since getOsSetting automatically loads it.
* restore unix overview graphs, they are different
small cleanups
* fix
* Device Cache
also some additional device related models
* attribs from cache
* replace common attribute functions
* remove legacy cache usage
tidy up some collection manipulation
remove some unused or single use functions
* cleanup some items
* always return a device, to prevent bugs
* clear device cache when testing after each test
* fix double assignment
* Clean up function to take advantage of null object
