* Enable content cache for state network.
* Update state json-rpc endpoints to return local content which uses cache if enabled.
* Add content cache metrics.
* Make content cache configurable.
* Add content cache tests.
* Add validation functions to be used in state portal rpc.
* Add validation to remaining state portal rpc methods.
* Lookup local content in recursiveFindContent rpc methods.
* portal_stateFindContent and portal_stateOffer no longer store in db.
* Create separate portal rpc handlers for each sub-network.
* Remove random gossip from history and state networks.
* Move shared portal rpc endpoints into common handler.
* Use enum instead of network string.
bhartnett
Kim De Mey