Adding ability to record and playback WAV files.

[nebbian]

This code adds the ability to record WAV files to the SD card, in a similar manner to how the record_ogg sample code works.

Unlike the record_ogg example, this uses the native IMA ADPCM encoding which doesn't require the loading of a patch file every time the user wants to record some audio. This results in a much faster response time, from the time that a recording is requested to be started, to the time that the system is able to actually start recording.

The example provided here has the following functionality:

• Connect to the VS1053
• Play a tone
• Connect to the SD card
• Wait for the button to be pressed
• While the button is pressed, save the recorded sound to a WAV file
• When the button is released, finalise the WAV file, and play it back immediately
• Go back to waiting for the button to be pressed

This code is based on the following sources:

• Adafruit Ogg Vorbis example: https://github.com/adafruit/Adafruit_VS1053_Library/tree/master/examples/record_ogg
• VS1053 datasheet located here: https://cdn-shop.adafruit.com/datasheets/vs1053.pdf
• TMRPCM code located here: https://github.com/TMRh20/TMRpcm/
• Adafruit forum post located here: https://forums.adafruit.com/viewtopic.php?t=50885