Adds a new 'hanlon_subnets' parameter to the Hanlon server configuration
(and uses that parameter to determine if a RESTful request submitted by a
user against the Hanlon server is from the Hanlon subnet).
Merge pull request #294 from tjmcs/tb/add-subnet-def-to-config

Fixes #293 (Users should be able to specify values for the Hanlon subnet)