Rename API entities to enhance compliance with the spec

[pavel-kirienko]

• canardEncodeScalar --> canardEncodePrimitive
• canardDecodeScalar --> canardDecodePrimitive
• CanardTransferTypeResponse --> CanardTransferTypeServiceResponse
• CanardTransferTypeRequest --> CanardTransferTypeServiceRequest
• CanardTransferTypeBroadcast --> CanardTransferTypeMessagePublication
• canardBroadcast --> canardPublishMessage

[pavel-kirienko]

From #99:

The function "canardCleanupStaleTransfers()" must be removed (this affects the API and the demo); see section 4.2.1 for details. This change to the spec was implemented in order to improve deterministic behavior at the cost of somewhat increased average-case memory usage (the worst case is unaffected). The constant CANARD_RECOMMENDED_STALE_TRANSFER_CLEANUP_INTERVAL_USEC is therefore not needed either (there could be other constants which we no longer need).

Data type signature must be removed from everywhere. This includes the callback signature CanardShouldAcceptTransfer.

The API functions still use "data type ID" instead of "subject ID" and "service ID", this should be fixed.

The transfer priority constants require updating. We have proper mnemonic names for the eight priority levels defined in 4.1.4.

The script show_data_type_info.py will no longer be needed, since there are no signatures to worry about.

[aasmune]

I have started working on this now but will wait to commit/push until #99 is merged.

[aasmune]

Fixed in #106