Mention I2PControl password option in README.

README.md

@@ -111,6 +111,7 @@ Cmdline options
 * --bobaddress=         - Address of BOB service, 127.0.0.1 by default (only used if BOB is on)
 * --i2pcontrolport=     - Port of I2P control service. Usually 7650. I2PControl is off if not specified
 * --i2pcontroladdress=  - Address of I2P control service, 127.0.0.1 by default (only used if I2PControl is on)
+* --i2pcontrolpassword= - I2P control service password, "itoopie" by default
 * --conf=               - Config file (default: ~/.i2pd/i2p.conf or /var/lib/i2pd/i2p.conf)
                           This parameter will be silently ignored if the specified config file does not exist.
                           Options specified on the command line take precedence over those in the config file.