upnpsoap: make subtitle support more generic

It sounds like more clients may support subtitles using a res element,
so we should make our support more generic.
clients: add Asus O!Play support and quirks

Asus O!Play reboots with titles longer than 23 characters with some
file types when there are subtitles present.  So we truncate video
file titles with external subtitles.

It also supports subtitles in LG fashion, so add that too.