Fixed GAMESTATE:GetCurrentStage to use correct logic for determining if all human players are on final stage.

THEME:GetPath lua functions can now pass true for the third arg if the element is optional.
Fixes to various StageDisplay things in default.
thify_number and thified_curstage_index lua functions added to default/Scripts/04 Other.lua.

src/ScreenGameplay.cpp

@@ -325,6 +325,7 @@ ScreenGameplay::ScreenGameplay()
 	m_pSongBackground = NULL;
 	m_pSongForeground = NULL;
 	m_bForceNoNetwork = false;
+	GAMESTATE->m_AdjustTokensBySongCostForFinalStageCheck= false;
 }
 
 void ScreenGameplay::Init()
@@ -928,6 +929,7 @@ void ScreenGameplay::InitSongQueues()
 
 ScreenGameplay::~ScreenGameplay()
 {
+	GAMESTATE->m_AdjustTokensBySongCostForFinalStageCheck= true;
 	if( this->IsFirstUpdate() )
 	{
 		/* We never received any updates. That means we were deleted without being