Review multitenancy

Due to PatternFly changes, in the new UI all accounts are called accounts (whether they are tenants or developers) see ThomasMaas message in #docs - 07DEC2018

Multitenancy is an onprem feature. The documentation can be found in: https://access.redhat.com/documentation/en-us/red_hat_3scale/2.3/html/api_bizops/multitenancy

A thorough review is needed to ensure accounts is used instead of tenants. Additionally, either remove or update the screenshots.