Rename some fields in channel class

[alexhutko]

Please feel free to ignore any of these suggestions if there's a conflict of standards or names present. I guess we could do channel_code, station_code, network_code, location_code.... but I think the following may be simpler (in my current frame of mind).

channel.code --> channel.channel
channel.network (remains same)
channel.station_code --> channel.station
channel.station_name (gets nuked)
channel.name --> channel.station_description (or station_fullname?)
channel.loc --> channel.location
channel.lat --> channel.latitude
channel.lon --> channel.longitude
channel.elev --> channel.elevation
channel.description (is this ever populated? I guess it can remain)