Initial commit of skeletons project
Delete skeleton files before Fiji attempts write

Fiji will not overwrite files by default, resulting in no-op calls to
Skeletonize 3D in Fiji. This commit fixes that by deleting any prior
output file before running the macro.
Call Fiji in headless mode to avoid stolen focus

Without the '--headless' option, Fiji would steal focus from any
running applications on each invocation. This is now prevented, and as
a bonus it will run on a cluster!
Process labels in decreasing size order

Since the labels are output every 10 processed labels, this will
result in more of the volume being processed faster, should the
procedure be terminated early.
Annotate background volume saving