Proper load/save support for Galaxy generator.
Always create new GalaxyGenerator to ensure clear state for new Galaxy.
Allow unexplored systems to become explored in game.
Persist explored state of a system.
Lua support for exploring systems.
Automatically explore system when entering it.
Ensure that cached sectors in FactionsDatabase consider persistent state.
Itty bitty tweak for vs2013 compiler, make two methods protected rather than private.
Merge pull request #3201 from lwho/system_exploration

System exploration