Fix typo in run tool
Make NETIO-230B power plug configureable
Increase flexibility for serial devices in run-tool

Instead of using a fixed command like picocom in the run tool,
it's better to have the flexibility to set the whole command that
connects to the serial device. Therefore, it's possible for instance
to connect to a remote serial device exported via TCP/IP by using tools
like socat.
Release notes for Genode 13.05