Merge remote-tracking branch 'origin/master' into ser-putcode-model

# Conflicts:
#	core/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.compact.wasm
#	node/runtime/wasm/target/wasm32-unknown-unknown/release/node_runtime.compact.wasm
#	srml/contract/src/account_db.rs
#	srml/contract/src/lib.rs
#	srml/contract/src/tests.rs