Version v0.05f

• Added missing Bluetooth OCXO warmup messages.
• OCXO warmup now a separate function from calibration.
• Added countdown for calibration (only reported on USB serial for now).
• Added selectable calibration countdowns (15s or 60s).
• A few comments improved / clarified.

Many thanks to iannezsp, this is basically a manual merge of his latest pull request + a few additions of my own.