Add library synnefo.util.units for parsing numerical values
with an optional unit suffix and printing integer values based
on a given style.

Styles `b', `kb', `mb', etc allow printing in the respective multiples
of byte, style `auto' in a human-readable manner, while `none' omits
units altogether.

Add option `--unit-style' in all astakos management commands that print
resource limits and quota usage. Consult the resource definitions to find
out which unit, if any, to show. For resources with unit `bytes', all
commands default to MB.