return None instead of raising KeyError
populate model lazily, working even when first call to list_instances fails
pass the instance id all the way down to the cloud server
show number of devices running on each cloud instance, fixes gns-34
signal when an instance was selected/deselected
select nodes running on the selected cloud instance
emit signal when table is clicked, not when selection changes
Merge pull request #41 from planctechnologies/gns-37

Gns 34 -  display the number of devices running on the instance
Merge pull request #42 from planctechnologies/gns-37a

Highlight devices running on instance
Merge pull request #40 from planctechnologies/gns-106

Gns 106 list_instance failure causes missing server instances
Merge pull request #140 from planctechnologies/pr1

Instance inspector improvements