By Anders Holst: Improve custlist editor

1. Show the current seek state next next to the service time.
  It is very convenient to see how fast one is winding, when scanning
  through a movie.

2. Don't jump away from the current position whenever a cut or mark is
  added or removed.
  2a. The variable self.last_cuts was not initialized, causing a jump
      to the first mark position when the first cut is made.
  2b. Search backwards for the first difference between old and new
      cut lists: After having produced a cut pair (out - in) you
      would like to end up at the end (in) rather than beginning
      (out). (This also gives more intuitive selected positions in
      the general case.)
  2c. Inhibit jumping whenever a cut or mark is removed: You don't
      want to leave that position now when it has no mark to easily
      jump back to.

3. Standing at either border of a cut, at IN or OUT, should always count
  as inside the cut, so that removing it is enabled from there.
  3a. Count standing exactly at the end of a cut as also standing
      in an "OUT" area.
  3b. It was not possible to remove a "cut from the beginning" at
      all if there was any mark before the "IN" point - it was not
      correctly recognized as an "OUT" area.

Also note that nowadays, with the more exact seeking code of Enigma2
(on both platforms, DM7025 and DM800/8000), the CutListEditor can't be
accused of being imprecise any more: As long as you put your cuts at
GOP boundaries (which you are most likely to do if you fine tune your
position with GOP single-stepping), the CutListEditor now has perfect
precision!  :-)

patch for #246