support/download: support -q in all download backends

Add an option flag to all backends, as well as the check-hash script, so
as to silence download helpers when the user wants a silent build.

Additionaly, make the default be verbose.

Inspired by Fabio's patch on git/svn.

[Thomas: fix a typo "Environemnt" -> "Environment"

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Fabio Porcedda <fabio.porcedda@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>