add general instance type managment to ec2FlavorPoller
add general instance type managment to ec2FlavorPoller

With this commit the flavor poller now checks on the local json files and makes sure they have been refreshed within the last 7 days.
If they have not a new version is downloaded then parsed into the ec2_instance_types table that will server as a springboard
to populate cloud_flavors when an amazon cloud has been added.

hep-gc/cloudscheduler,hep-gc/cloudscheduler,hep-gc/cloudscheduler,hep-gc/cloudscheduler