Add CLI flag for raw packet output

[CBielstein]

Description

Frequently during development, I want to see raw packets of a certain type. To achieve this, I find myself commenting out the code to print out decoded packets (the PrintPacket method) and adding in an explicit console write for any string received by the AprsIsClient.ReceivedTcpMessage event.

This issue should add this capability as a command line switch. Consider -r and --raw. When those are present, the output should be all raw messages from the server and should disable the decoded output.

This should be possible by checking parameters and swapping out the existing event handling registration for a simple handler that writes to console for any events on AprsIsClient.ReceivedTcpMessage.

Acceptance Criteria

• New flags to command line AprsIs app: -r and --raw to toggle raw output mode and disable the decode
• Ensure documentation for the new flag shows up in --help output
• Functionality to disable decode and print and enable raw output when that flag is present