TS: IpFilter and Deproxy refactorings

IpFilter:
 - filterIpAddress method now tested and accepts optional Headers
   argument, X-Meresco-Ipfilter-Fake-Ip header now supported here too.

Deproxy:
 - Allow initializing without deproxyForIps / deproxyForIpRanges.
   This is useful when configuration is dynamically set using the
   updateIps method.
 - X-Meresco-Ipfilter-Fake-Ip header is delegated to Deproxy's internal
   IpFilter; Deproxy can now be easily integration-tested.
 - Observable name init pass-through.