Add SMX mode support

[Horsey-]

things I fixed:

• positioning misalignment on ScreenSelectStyle
• added a StepmaniaX logo to ScreenTitle
• updated the test input graphic
• cleaned up a few extra newlines
• added and cleaned up some comments
• added helptext in the operator menu game selection screen

[Horsey-]

This has been merged with slight modifications and additions in a separate commit.