buffer_autoset.py treats channel names case sensitively

[jlu5]

For example, setting a config entry like buffer_autoset.buffer.irc.somenet.#Lobby.short_name treats the channel name, #Lobby, case sensitively.

The annoyance of this is that when the channel on somenet turns out to be a different case (such as #lobby), buffer_autoset options fail to apply. Also, setting another entry named buffer_autoset.buffer.irc.somenet.#lobby.short_name without removing the old one refuses to work because the configuration DB is case insensitive.