support/graph-size: add option to sort packages in reverse size order

support/graph-size: add option to sort packages in reverse size order

Currently, the packages are sorted smallest first, and biggest last
(with unknown and others second-to-last and last, resp.).

Add an option to invert the ordering (but keeping unknown and others at
their current positions).

This has the nice side effect that we can now control the colours
assigned to the biggest package(s), as the colours are cycled from the
first to the last. Currently, the biggest packages gets a redish colour,
which is appropriate, but the second gets a greenish one, which is not
as appropriate (but changing that can come later).

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>