Independent timeline for Movie Clip Editor.

When editing video, it is not convenient sincronize the scene time with the Clip player. An independent timeline to reproduce the Clips and adjust the length and speed of these I think itwould be the right thing. The Clip Editor timeline should be able to ynchronized with Scene Time in Trackings and other cases, but not always. Also Clips in Clip Editor should be possible to synchronize with the parameters of the Input/MovieClip in Composer Editor node.