Merge 'origin/master' into ser-contract-ioc

# Conflicts:
#	demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.compact.wasm
#	demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.wasm
#	polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm
#	polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm
#	substrate/runtime/contract/src/lib.rs
#	substrate/runtime/staking/src/genesis_config.rs
#	substrate/runtime/staking/src/lib.rs