Merge branch 'ethersphere-frontier/natspec' into develop

cmd/geth/js.go

cmd/geth/main.go

cmd/utils/flags.go

common/bytes.go

common/docserver/docserver.go

common/docserver/docserver_test.go

common/natspec/natspec.go

common/natspec/natspec_e2e_test.go

common/natspec/natspec_js.go

common/natspec/natspec_test.go

common/resolver/contracts.go

common/resolver/resolver.go

common/resolver/resolver_test.go

core/genesis.go

eth/backend.go

rpc/api.go

xeth/frontend.go

xeth/xeth.go