Merge StageResults into PlayerStageStats. Move results calc into StageStats.

This makes StageStats touch some stuff that I don't think it should, but it's
an improvement over having all this scoring logic inside a special screen.

stepmania/src/PlayerStageStats.cpp

@@ -42,6 +42,10 @@ void PlayerStageStats::Init()
 
 	m_pdaToShow = PER_DIFFICULTY_AWARD_INVALID;
 	m_pcaToShow = PEAK_COMBO_AWARD_INVALID;
+	m_iPersonalHighScoreIndex = -1;
+	m_iMachineHighScoreIndex = -1;
+	m_rc = RANKING_INVALID;
+	m_HighScore = HighScore();
 }
 
 void PlayerStageStats::AddStats( const PlayerStageStats& other )