including temporary reference to local snapshot version of the pi4j-mock-plugin.

this means that the class is updated to pi4j V2 and supports multiple chips on the same SPI bus in one single commit.
Commit isn't functional (still depends on pi4j Component parents log() and delay() methods) but useful to see what has been affected.

gradle build now successfully compiles

Mainly used to assertArrayEquals without having to punch in hundreds of magic numbers.
Also used to fill the MockSpi.raw data buffer with prepared data.

add Mockito dependency

...according to https://github.com/junit-team/junit5-samples/blob/r5.10.0/junit5-jupiter-starter-gradle/build.gradle

…s() factory method.

…oader doesn't support cross-workflow artifact sharing

…ne of those kind of method sets.

NOTE: the current implementation doesn't allow for multiple separate instantiations of chips or chip arrays with the static factory methods because the SPI id is hardcoded. Will have to fix during refactoring. That's the reason method coverage isn't 100%.

…Makes it way more configurable.

NOTE: the added flexibility might pose a difficulty obstacle for the user. Could maybe be mitigated by providing examples.

…s DI-ed.

This removed some pretty ugly code duplication. yay!