cache: reimplemented auto-caching

Implemented a smarter auto-cache that's context sensitive. Caching will
automatically pause when playback begins or values are being changed and resume
when inactive.

app/render/framehashcache.cpp

@@ -135,6 +135,11 @@ QList<rational> FrameHashCache::GetFrameListFromTimeRange(const TimeRangeList &r
   return GetFrameListFromTimeRange(range, timebase_);
 }
 
+QList<rational> FrameHashCache::GetInvalidatedFrames() const
+{
+  return GetFrameListFromTimeRange(GetInvalidatedRanges());
+}
+
 void FrameHashCache::SaveCacheFrame(const QByteArray& hash,
                                     char* data,
                                     const VideoRenderingParams& vparam)