Running multiple StackReg in parallel does not work

[tischi]

Due to this file staging:

StackReg/src/main/java/StackReg_.java

Line 1021 in 9ee280f

final FileSaver sourceFile = new FileSaver(source);

...files from different processes will overwrite each other and create a very messy output.

One could try fixing this by giving more unique file names, e.g. using some random numbers.

[imagejan]

/cc @dasv74