Automatically generate node names

[jc064522]

Node names are currently set manually in config. When deploying another Stroom 6 node this is currently the only item of configuration that needs changing. If nodes had automatically generated names then this step wouldn't be necessary.

Resolving this issue, in combination with gh-644 (automatically generate cluster call URLS), would mean scaling could be much more automatic and potentially zero-configuration.

[at055612]

Relates to #2121