alpha.7 upgrade

[ETeissonniere]

Context

Bump all deps and code to be alpha.7 enabled.

Fixes #88.

Caveats

• benchmarks don't seem to compile fine anymore
• strange build error when using benchmarks with pallet-emergency-shutdown Error when testing emergency shutdown pallet with all features #105
• wasmtime unsafe calls? Re-enable wasmtime #106

Sanity

• I have incremented the runtime version number

Quality

• I have added unit tests, and they are passing
• I have added benchmarks to my pallet
• I have added the benchmarks to the node
• I have added comments and documentation

Testing

• The node runs fine on a development network
• The node runs fine on a local network
• The node runs fine on an upgraded local network
• The node can synchronize the existing network