Topology refactor / Standalone mode

* Centralizes as much of the topology logic as possible into the `TopoHelper` class (in `ec-common/libraries/topo_helper.rb`)
* Enables standalone topology (actually works)
* Support Analytics node in a much less hacky way
This could be done slightly more elegantly with combined_topo = TOPO_TYPES.select { |layer| layer_exists?(layer) && include_layer?(layer) }

No problem with the way you have it though.

Merged topo could just be:
found_topo_types.map { |layer| @ec_config[layer] }.reduce({}, :merge)