-Change: move the AdminConnection to its own file

-Add: documentation for various functions
-Change: replaced kwargs to __init__ with properties
-Fix: missing import
-Change: increase the read timeout

-Change: use .configure for the configuration.
-Add: silence logging
-Add: experimental support for the SERVER_RCON_END packet (even though
we don't support that packet yet) in the openttd-admin-rcon.py command.