Allow custom LoRa boards about lora-phy

[ceekdee]

Providing a RadioKind trait with default implementations and allowing a proprietary implementation to just extend certain RadioKind trait default functions runs the risk of causing the proprietary implementation to fail if enhancements are made to the default implementations without knowledge of the ramifications to the proprietary implementation. It becomes difficult to do a semver assessment. Therefore, my current inclination is to encourage developers of a proprietary RadioKind implementation to implement all functions separately to provide isolation from minor changes to the base implementation.

However, as areas are identified where more flexibility is needed, the relevant functionality will be enhanced to allow parameterization (possibly trait-based) that enables that flexibility. Currently, the RadioKind set_oscillator() function seems ripe for better parameterization.

[ceekdee]

Addressed in v2.0.0.