* Add missing `As` imports.
* Adds new API traits that will be used by the client and runtime
* Switch consensus to new API's
* Switches transaction-pool to new API's
* Move runtime api stuff into its own crate
* Adds `impl_apis!` macro for implementing the new API traits
* Make `metadata` return directly a blob
* Runtime replace `impl_stubs!` with `impl_apis!`
* Switches to none feature based approach for declaring the different API traits
* Fixes compilation error
* Fixes errors
* Make the `decl_apis!` trait usable from the outside
* Make the `test-client` use the new API traits
* Remove last `impl_stubs!` bits and move some of them into wasm executor for tests
* A little bit more documentation
Bastian Köcher