[HACKTOBERFEST] Examples

[MMMMMNG]

Adds examples to the project

As hinted at in 2d9a118 :)

Changes

• New source set: 'examples', compiles to an executable fatJar with the compiled MCP23S17 class included (so it mimics a third party app trying to use this class)
• New task: runExamples takes the executable fatJar, puts it on the pi and runs it.

TODOs

• add example where chips are used as outputs rather than inputs (or mixed maybe?)
• test with actual chips and wires connected and all

Future TODOs

• refactor the static factory methods to some kind of builder class or something, 'cuz the way it works now there would have to be a new method for every combination of enabled interrupt pins and enabled hardware address pins which doesn't seem very DRY.