Defaults, empty map loading, cleanup, bugfixes

- Finally moved isSP from Config to Basic
- Removed string conversion for certain types
- Added defaults for Basic, Lighting and SpecialFlags
- Added a new list that provides MultiplayPassive countries only (used
in MP maps for objects)
- Implemented loading of MultiplayerDialogSettings for reading TechLevel
max
- TechLevel list is now dynamic since the max is settable
- Started work on creating a "New map"
- Fixed issues with Countries
-- Local Countries are erased after loading in MP maps
-- Color key is deleted for a Country if it doesn't share the same name
as a House
- Writing an INI section completely only happens if it has content, this
prevents empty sections with merely the ID written