Create a config to specify one-time prices and corresponding coupon
ids for partners.
github issue: https://github.com/storj/storj-private/issues/118
Change-Id: I67b26e7208b12ba8f0e6dc1b164dd9545b09cac0
This change allows for overriding project usage prices for a specific
partner so that users who sign up with that partner do not need their
invoices to be manually adjusted.
Relates to storj/storj-private#90
Change-Id: Ia54a9cc7c2f8064922bbb15861f974e5dea82d5a