Pine64 Clusterboard Casing

Another spin-off from the android i'm working on: a Casing for the [soPine64 Clusterboard](https://store.pine64.org/?product=clusterboard-with-7-sopine-compute-module-slots)

20190707: More adjustments for the PCB space. more room on X,Y,Z and DC and Ethernet Connector holes did not match.
20190706: after printing upperA, adjusted the internal space by 2mm. the clusterboard did not quite fit.