Command-Line: add a flag to suppress showing the progress

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Command-Line: suppress too fine-grained progress

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Command-Line: suppress checksumming progress in Jenkins jobs

... or for that matter, any time we're redirected...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'cmd-line-progress'

This branch fixes https://github.com/imagej/imagej-updater/issues/19:
the checksumming output no longer dominates the output of redirected
shell scripts (such as used in Jenkins).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>