* Make `decl_runtime_apis!` implement `RuntimeApiInfo` for all runtime
apis
* Make the runtime side generate the info constants as well
* Make `RuntimeApiInfo` implementation use the correct generics
* Adds a test for the runtime api info stuff
* Remove duplicated code by using block from `test-client`
* Adds `compile_fail` tests for `api_version`
* Adds documentation for `api_version`
* Make `impl_runtime_apis!` generate `RUNTIME_API_VERSIONS`
* Update documentation and tests for `RUNTIME_API_VERSIONS`
* Implement `has_api` by using the `RuntimeApiInfo`
* Make `impl_runtime_apis` check that trait identifiers are unique
* Prefix all runtime api function with the corresponding trait
So `execute_block` will be called `Core_execute_block`.
This makes it possible to have traits implement a function with the
same name.
* Rebase master
* Update after master rebase