* don't check interface ips when getting ips from dns pool
* assign dns ip range to loopback instead of one-ip-at-a-time
* recycle unused dns ips
* replace $dst_hostname when calculating dial identity
* fall back to dummy resolver if server initialization fails.
- Rename host.v1 dialIntercepted* properties to forward*
- Add allowed* properties to whitelist destinations that are dialed via forward*
- Add allowedSourceAddresses, which serves as a whitelist for source IPs/CIDRs and informs the hosting tunneler of the local routes to establish when hosting a service
* use shared network IP range for services that are configured with unresolvable hostnames
* parameterize dns intercept IP range
* reuse utils.incIP
closes#339
Shawn Carey