Create constants for byte messages, implement asbytes so many methods can take Message and key objects directly and split get_string into get_text and get_binary. Also, change int handling to use mpint with a flag whenever the int is greater than 32 bits.

Conflicts:
	paramiko/proxy.py

fix convoluted logging method

bug 200416:
don't create a new logger for every channel and every sftp client or server.
it causes python to leak lots of useless logger objects, because they never
go away. instead, log the channel # in the message, and use only a couple of
standard log nodes.

bump copyright year to 2007