Even more sugar for static inports (constant senders)

[emil14]

This idea is kinda in same spirit as #591

Before

Explicitly send 42 to foo:b

flow XXX(data) (sig) {
  nodes { Foo }

  42 -> foo:a
  :data -> foo:b
  foo:sig -> :sig
}

After

"Set" a to 42 and omit it in network completely

flow XXX(data) (sig) {
  nodes { Foo(a=42) }
  :data -> foo:b
  foo:sig -> :sig
}

Questions

• = or : syntax?
• will it play well with #564 ?
• can one set all inports?