Docker support for raspberry pi (arm)

[JayNewstrom]

Right now I get the dreaded standard_init_linux.go:228: exec user process caused: exec format error

[JakeWharton]

Yep yep. PR welcome for it, or I'll get to it eventually.

[JakeWharton]

I rewrote the app in Kotlin/JVM, so you can now run it standalone anywhere you can get a JVM.

I will leave this open, however, because we should vary the Docker container still. Plus I might switch it to Kotlin/Native...