Rename Bluetooth stack function parameters to clearly indicate what sort of Bluetooth channel (ACL, RFCOMM) is required for each parameter, to make the code easier to read.

Add a new RFCOMM_ChannelSignalsReceived() Bluetooth stack callback from the RFCOMM layer for when the remote device sends new terminal control signals.

Fix RFCOMM_SendData() not aborting correctly when the requested RFCOMM channel is not found.

Add a new RFCOMM_ChannelOpened() callback event for when logical RFCOMM channels are opened in the BluetoothHost demo. Make the demo echo back sent characters to the remote device.

Move out Bluetooth stack callback functions to a seperate BluetoothEvents.c/.h set of files for clarity in the Incomplete BluetoothHost demo. Add a new stack callback for opened ACL channels, make the demo save the RFCOMM channel when opened so that it does not have to search for it on each iteration of the main program loop.