movistar_epg.py: slightly breaking change for recordings, best to

erase the old "recordings.json" and start over. Keep the timestamp
of the recorded programs instead of the pid, just like the epg itself
does. The pid is something ephemeral of little use after some time,
whereas the timestamp can be useful ever after.

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