Replace "caprice" with a "showcourse"/"noshowcourse" tag.

This also allows hiding static songs; I added that since it took about four
lines extra code.

Note that I've updated the Save() function a bit, and fixed some bugs
I saw, but it's not used yet and it's no more tested than it was before.

stepmania/src/BPMDisplay.cpp

@@ -187,7 +187,7 @@ void BPMDisplay::SetBPM( const Course* pCourse )
 	vector<float> BPMS;
 	for( unsigned i = 0; i < ci.size(); ++i )
 	{
-		if( ci[i].Random )
+		if( ci[i].Mystery )
 		{
 			BPMS.push_back( -1 );
 			continue;