Improve handling for example calibration data on fresh setup

[ogeesan]

In #42 the UIs were not properly triggered because the COM port field is absent. This PR:

• Creates a function that populates the example data, increasing testability of the data.
• Uses a special case "example data" COM for the example data which is recognised as being non-user data during COM match check.

This ensures that UI warnings about COM mismatch are not triggered if the user is yet to even touch the liquid calibration data.

Note that the warnings concerning "old calibration" were turned off in bc33156 until a UI to opt in is built.