Create LevelGroup.cs.
Merge branch 'master' into level-group
Merge branch 'master' into level-group
Merge branch 'master' into level-group
Add Load and Save methods, and create the level list.
Remove unused using statements and commit the .contentproj file.
Implement resource path switching depending on Debug or Release configuration.
Don't hardcode the file name in Save().
Merge remote-tracking branch 'jorenz/level-group'