RFR: JDK-8053907 - Provide Sample Service Provider

[Jen Dority]

issue: https://bugs.openjdk.java.net/browse/JDK-8053907
webrev: http://cr.openjdk.java.net/~jld/8053907/

Hi All,

Need a review for these changes which provide a sample showing how to 
use the DIO APIs to create a service provider to define custom devices. 
The device used in the sample is an MCP3008 ADC chip, which uses SPI 
(Serial Peripheral Interface) to communicate.

Thanks,
Jen