Merge pull request #2965 from fjl/swarm-merge

contracts/chequebook/cheque.go

internal/web3ext/web3ext.go

swarm/api/api.go

swarm/api/api_test.go

swarm/api/config.go

swarm/api/config_test.go

swarm/api/filesystem.go

swarm/api/filesystem_test.go

swarm/api/http/roundtripper.go

swarm/api/http/roundtripper_test.go

swarm/api/http/server.go

swarm/api/manifest.go

swarm/api/manifest_test.go

swarm/api/storage.go

swarm/api/storage_test.go

swarm/api/testapi.go

swarm/api/testdata/test0/img/logo.png

swarm/api/testdata/test0/index.css

swarm/api/testdata/test0/index.html

swarm/network/depo.go