Rename Signals methods

[Thomasdezeeuw]

Current Signals has the following two methods:

• Signals::receive -> returns a single signal.
• Signals::receive_signals -> returns multiple signals.

Rename them to:

• Signals::receive -> returns multiple signals.
• Signals::receive_one -> returns a signal signals.

To reflect to common use case better.

[Thomasdezeeuw]

Not worth it.