Added DisplayInstanceIdentifier to HostInformation

The `HostInformation` class needs 3 default pieces of information about a host:
- HostId -> the unique identifier of an endpoint host instance
- DisplayName -> This is the Environment.MachineName for most scenarios except in Azure it will be RoleInstance
- DisplayInstanceIdentifier -> This is a string that uniquely identifies an endpoint instance, eg ProcessId or path to exe or windows service name, this is to be displayed on UIs, such as SP and SI