Normalize terms used throughout the codebase.

[AlejoAsd]

Different objects are called various names throughout the code. I'm opening this issue to converge on some names and update the codebase accordingly.

The three main objects we need to name are:

1. Signals sent by the operator.
2. Signal Arrows.
3. Groups of signal arrows.

Some terms I found sprinkled everywhere:

• Signal → Usually used for Signals sent by the operator.
• Transmission → Used for both arrows and signals sent by the operator.
• Pattern → Usually used for Signal Groups.
• Morse → Usually used for Signal Arrows.