discovery of mdns urls
broke out mdns logic into its own class
added license text to mdns class
implemented recommendations pt 1
discovery service simplification

Matched the pattern used in NearbyBeaconsFragment for ble scanning.
added mdns to UribeaconDiscoveryService
implemented comment recommendations
removed unused imports
Merge pull request #226 from matthewsibigtroth/mdns_urls

discovery of mdns urls