* Adds new wrapper traits for wasm executor
* Add new crate `substrate-wasm-interface`
Thew new crate holds types and traits for the communicating between the
wasm runtime and the host.
* Rewrite externals with new macro etc
* Fix vec initialization
* Make executor tests working
* Remove unused code + warnings
* Introduce `Pointer` and `WordSize` for working with wasm
* Fix tests and compilation
* Fix compilation
* Apply suggestions from code review
Co-Authored-By: Sergei Pepyakin <sergei@parity.io>
* Review feedback
* Remove unused conversions
* Make each host function its own struct
`HostFunctions` now just returns these function structs. Each function
can be executed by using one of the function structs. The inherent host
functions are now moved to the "normal" host functions.
* Remove byteorder
* Add floating point types
* Make pointer interface more safe
* Add type alias for wasm-interface Result
* More review comments
Bastian Köcher