Short form for self ports in network

[emil14]

in:enter -> out:exit

=>

:enter -> :exit

[emil14]

or even simply enter -> exit

Looks like we don't reserve this form yet:

node:port -> // normal port addr
$constRef -> // constant reference
42 -> // constant (primitive) literal (int)
42.0 -> // constant (primitive) literal (float)
"42" -> // constant (primitive) literal (string)
true -> // constant (primitive) literal (boolean)