[Broker-J]Misleading Documentation of "Node Priority" for the initial configuration

User Story

As a developer, I want to easily create a HA cluster by just reading the documentation.

State of Play

In order to configure a Qpid Cluster, you got the following hints:

1) Create it in the web UI - it requires a lot of clicking and is (in my opinion) not the way as devOps guy would want to setup a cluster 

2) Use the initial configuration

Besides all the missing information of what can be actually configured in this initial configuration,
the following property is completely miscommunicated: Node Priority.

The following page] states, that this configuration property can be represented by the values "Highest", "High", "Normal", "Never".

And yes, this configuration can be set in the web UI - however, it is rather hidden. And of course, these values don't work inside the initial configuration. 

So let's take a look into the actual API documentation, which is unfortunately only available, when you have already a running broker available (http://localhost:8080/apidocs/latest/virtualhostnode):

BDB_HA Specific Attributes

This API doc states that the priority is of type number - and again: setting a number as priority is not working.

However, the actual configuration (that works) looks as follows:

{
  ...
  virtualhostnodes: [{
     ...,
     priority: "2"
     ...
  }]
  ...
}

As you can see, it is a stringified number ("2") whereas a pure number isn't working (2).

Steps to achieve victory

 Add a subchapter in the initial configuration that states how to configure a HA cluster by just using the initial config file.

 Add a complete documenation of any configuration property