Serial port device user configuration

[wickwire]

• Serial port definition in mariner is currently hard-coded at mariner/mars.py
• This is to be expected since mariner targets the Raspberry Pi Zero W as the microPC board to use
• This also limits the use of other similar microPC boards or actual PCs using serial<>USB adapters, to achieve the same functionality - in the sense that there is no guarantee that the serial port device is to be the exact same
• This issue is about providing an easy means of configuring the serial port device via the Web UI, without the need to edit code

[wickwire]

First consideration on this should be a simple, stupid approach by attempting to scan all available serial port devices on the system and then listing them in the web UI, using a drop-down list or similar UI component to allow selection;

• add baud rate configuration (drop-down list also)
• add button to save the desired configuration

Will be looking into pyserial for testing this out.