Add support for usage of existing named Service Bus Namespace

[HenrikSommer]

Creation of Service Bus Namespace is a timeconsuming task in Azure, thus using an existing named Service Bus Namespace is preferable to achieve high speed integration testing. On the other hand it is preferable to avoid manual setup of Service Bus Namespaces in Azure.

The solution could consist of the following:

• When a named Service Bus Namespace exists within resource group it will be used as is
• When a named Service Bus Namespace does not exist within resource group it will be created