add the ability to pass arguments to kr/kd

For example, `kr "p /testbin/add; exit"` will run
sys161 "p /testbin/add; exit"
which tells the kernel to run `p /testbin/add` without prompting
you to enter a command to the OS via stdin.
Merge pull request #2 from jaredp/master

add the ability to pass arguments to kr/kd