movistar_u7d.py & movistar_epg.py: expose new vod only m3u playlist

for local recordings when the env var RECORDINGS is defined with the
local folder where recordings done by this backend should be stored
and now the folder whose content will be offered indexed in both
/recordings.m3u & /grabaciones.m3u endpoints.

Hence, even if the timers feature for automatic recordings of programs
is not used, just by defining RECORDINGS, its movies (files which end
in ay of ['.avi', '.mkv', '.mp4', '.mpeg', '.mpg', '.ts']), the m3u
will be updated every 5 minutes. All  entries include a logo if one is
found and content is grouped by folders, hence tv series.

This works amazingly well with TiviMate, adding a new vod only provider,
i.e. with no live channels. Content shows up in the Movies tab, with
all the groups being really easy to access. All in all, it works really
really well.

Curious thing was TiviMate, thus Android's ExoPlayer, plays streams
as Chrome do, i.e., to be able to seek/forward the video, the server
needs to offer Content-Rage support, which turned up really simple to
implement, and it performs as well as nginx itself, if not better, I
haven't measured it, it barealy consumes any cpu and it is really low
latency.

The only caveat with respecto to TiviMate is it does not show dvbsubs
when played from this vod m3u, unlike everywhere else, where they are
shown just fine.

Signed-off-by: Javier Marcet <javier@marcet.info>