CLI improvements for reseller system setup
Summary:
Limit non-scalpel list commands to the tenant context
Add CLI tool to list SKUs
Add scalpel:sku:update command
Improve user:create for resellers
Update RESELLER.md
Test Plan: ./phpunit
Reviewers: #hkccp_developers, mollekopf
Reviewed By: #hkccp_developers, mollekopf
Subscribers: #hkccp_developers
Differential Revision: https://git.kolab.org/D4707