Add some playlist functions

iteminfo: Use infopanel.

status.xml : add "seek" command
vlm, refresh.png : add refresh buttons (page doesn't autorefresh)

share/http/* : display instances for vlm media elements
               some layout changes (inputs and outputs)

preview display in the top left corner of the screen.

                              (instead of stoping after a depth of 2)

src/misc/vlm.c : minor instance information reporting change

 misc/vlm.c : export some p_input variables (state, position, time, length, rate, title, chapter and seekable) when using the vlm "show (media)" command.

support javascript.

Some files uses an empty (only holding a space) subtitle to mark the end of
the previous subtitle. These caused a little gray box to appear with
--freetype-effect 3 before this change

Should fix issues when schedules add or delete new schedules. Closes:#510

Also fixes a minor memleak in schedule creation/deletion

This is a quick hack, which should in the end be merged in a way to expose stats

* AccessOutWrite can be called with input already detached (Closes:#523)