allow access to special://skin through the webserver's VFS handler
[rbp/omxplayer] Fix leak when playing multiple files from playlist

When omxplayer plays a second file from a playlist (i.e. without being shut down) a clock component gets leaked.
Eventually enough of these leaked components will stop further playback
Merge pull request #3703 from popcornmix/clock_leak

[rbp/omxplayer] Fix leak when playing multiple files from playlist
Merge pull request #3697 from Montellese/getmatchingsource_skin_path

allow access to special://skin through the webserver's VFS handler
add missing startpos option to pydocs