Playback/Skipping fixes / cleanup by A. Holst

* Jumping between marks in the movie, with "<" and ">", doesn't work
  well when there are cut marks in the movie. Especially jumping
  backwards will fail if there is a mark in a cut out region that is
  to be jumped over. (InfoBarGenerics.py, chunks 3 and 4)

* Now when rewind works at all platforms also at low speeds, the
  rewind speeds x2 and x4 should be added again to the
  default. (UsageConfig.py, chunk 1)

* Cleanup some obsolete code: SeekBackHack and non-smooth
  winding. None of these can be used anymore, but remnants were left
  in the code and in the configuration alternatives. It is high time
  to clean these out. (setup.xml, UsageConfig.py chunk 2,
  InfoBarGenerics.py chunks 1 and 2, DVDPlayer)

* In the position gauge of the movie player, marks in the movie are
  shown as red dots. Long time ago the last position was also shown as
  a red dot, which was bad because it was confused with the marks, so
  it was removed. However, jumping between marks in the movie with "<"
  and ">" also stops at the last position, which is useful e.g. if you
  don't automatically start playing from the last position. The code
  below adds the last position back to the position gauge as a green dot,
  to distinguish it from the red ones. (epositiongauge.cpp)

refs bug #570