Set options from defaults on first start

Data/GenericData.dat specifies what the default values for some options
should be. Respect them on startup if the options in config are unset.

internal/assetstore/assetstore.go

@@ -35,6 +35,7 @@ type AssetStore struct {
 
 	// These members are used to store things we've already loaded
 	fonts   map[string]*Font
+	generic *data.Generic
 	maps    map[string]*Map
 	menus   map[string]*Menu
 	objs    map[string]*Object