Change apply when playing and add OPTIONS requirement

modules/FrameDifference.cpp

@@ -37,7 +37,6 @@ FrameDifference::FrameDifference()
   m_pchModuleTooltip = "Measure the difference between two images (Y plane),  Y1 - Y2, with max absolute diff of 128";
   m_uiModuleRequirements = MODULE_REQUIRES_NEW_WINDOW;
   m_uiNumberOfFrames = MODULE_REQUIRES_TWO_FRAMES;
-  m_bApplyWhilePlaying = APPLY_WHILE_PLAYING;
 
   m_pcFrameDifference = NULL;
 }