WIP Add new timeline states to try and bring in line with new API

[dalehamel]

WIP trying to pull in changes from plexinc/plex-media-player@304f4da

The upstream commit seems to indicate that the "stopped" signal to the media server is now invalid, as the server needs to know if it was "finished" or intentionally cancelled.

It's unclear if the "cancelled" signal actually needs to be emitted, but it probably does for the server to behave properly.

To start with, I've just replaced most instances of STOPPED with FINISHED, to try and simplify the patch.

I won't know if this has been effective until I've had a chance to try it out. I'm building a new version of OpenPHT-Embedded based on LibreELEC.tv 9.0.1, which should also bring in proper RPi3b+ support.

I may try and cut a release of the new OpenPHT changes alone, as users of the current stable builds would benefit from a build based on 1.8 more closely, with just the timeline changes. It's unclear what instabilities LibreELEC 9.0.1 may bring in (and which bugs it may fix).

[dalehamel]

The LibreELEC branch this is being built with is here RasPlex/OpenPHT-Embedded#2

[ukdtom]

Notice: https://forums.plex.tv/t/plex-server-1-15-3-858-and-above-broke-save-resume-on-opht-orca-and-other-plex-players/396505/52

[dalehamel]

thanks for sharing @ukdtom !

I still plan to get a new build out for testing within the month, and moving to the new API probably avoids quirks better going forward.

It's great that there will be a workaround in a new server version handled by plex server-side. Thanks @elan !