Backported the hp_core_spec.
Added maximum TTL enforcement also to MDNS client used in hp. By
default it's same as the one in hp_core. Now it's possible to have
mdns records also expire in a limited amount of time.
Merge branch 'vancouver' of github.com:fingon/hnet-core into vancouver
Added is_empty check.
Added if_active event to mdns_core.
Fixed is_empty event. Serious brainfart ongoing (is_empty utility + is_empty event = not win).
Made autodiscovery happen once a minute + added debug message.
Implemented OSPF tree changes based on if_active from mdns_core.
Added activity tracking to the testcase.
Merge branch 'vancouver'

Conflicts:
	hp.lua
	mdns_discovery.lua
	mdns_if.lua
	spec/mst_spec.lua