added another channel `/dev/script`

some Python users were unhappy with no dedicated channel for scripts
added `/dev/script` as a dedicated script channel
the default co-location logic was adjusted to not use `script` channel as a co-located object
if you still want it to be co-located for some strange reason you can use `"attach": "script"`

P.S. I'm considering to use `"attach": "none"` as a default behavior for nodes with just a `script` channel
but let's wait and see
Merge pull request #80 from pkit/script

added another channel `/dev/script`