Update ubiquiti_airos_

Version history:
v0.6 - added wlan errors by type graph - useful to detect interferences on the same frequency; added CPU usage graph
v0.5 - added ping graph - ping times from the AirOS device to a configured address; other fixes
v0.4 - corrected memory size unit calculation and display, fixed query bug, fancier graphs for memory and link speed
v0.3 - added undefined values handling in case of connection timeout, corrected linefeed character handling
v0.2 - combined all the separate pugins into one multigraph plugin, a couple of charts separated
v0.1 - initial version, separate plugin for each graph, packaged 11 different plugins