Made MetaGenerator a singleton via private constructor + getInstance().
First step on move to a stand-alone metadata server.
Added metadata.NetworkKey
Cleaned up MetaGenerator so that it loads an individual SeedVolume
for each network found, and can parse these to return a
List<Station> getStationList() that can be used to drive SeedScan
More clean up of MetaGenerator and added main() to make it stand-alone.