Merge branch 'master' into red-tests-#111

cmd/geth/main.go

cmd/geth/usage.go

cmd/utils/flags.go

core/blockchain.go

core/types/derive_sha.go

core/types/derive_sha_test.go

docs/programmers_guide/guide.md

eth/backend.go

eth/config.go

trie/resolver.go

trie/structural_2.go

trie/structural_test.go