Document human-readable size suffixes

Document human-readable size suffixes

Document that the quotas passed to fs setquota, vos create, and vos
setfields and the size passed to fs setcachesize may take a suffix
indicating the unit.  This documents the change in behavior implemented by
54c0a3f3e6575fa5af39ddd797d5381c36b48001.

Fix a copy/paste error in the vos create -maxquota option definition.

Reviewed-on: http://gerrit.openafs.org/212
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>