Picarto.tv plugin needs url update.

[julianrichen]

Currently livestreamer only supports

https://picarto.tv/live/channel.php?watch=<channel>

However the following are also acceptible:

https://picarto.tv/live/channelhd.php?watch=<channel>
https://picarto.tv/live/multistream.php?watch=<channel>

I belive the following regex should fix picarto.py:

_url_re = re.compile("""
http(s)?://(\w+\.)?picarto.tv/
live/(channel|channelhd|multistream).php
.+watch=(?P<channel>[^&?/]+)
""", re.VERBOSE)

I would create a merge request but I know very little about Python or compiling/testing it.