Implement node endpoints (#226)

* Create NodeNetwork

* Setup node/version

* Add unit tests

Test node transaction pool

Test node version

Add return types for services

* Shorten method names

* Superficial fixups

* Update NodeNetwork
docs

* Update docs and add pool field to transaction-pool

* save

* Update network return fields

* Update tx pool

* Update testing for transaction pool

* Update transaction pool docs

* Update docs

* Update openapi

* update readme

* Update clientVersion

* Update docs and network response property order

* Update transaction pool docs'

* Trivial changes

* Update import

* Link to node controllers from paths in README.md