Fix default value of color_space
Wait until Systray's window created when creating Systray
BugFix: left click on Systray may show wrong properties pages if more than one filter that exposed IDirectVobSub interface
Do NOT use IDirectVobSub in Systray code for it may not support by XySubFilter
Refused to join the graph if CDirectVobSubFilter has joined
Keep VSFilter away when join the filter graph by changing it's load level to disabled. And we'll restore it's load level as soon as we can (the first time the graph pause or when we leave the graph)