Add support for instructions load_i, load_si16, load_si32, and load_ui8

See merge request !119

Add CleanHeapValue to supporting JavaScript to be able to pass a deserialized value as an argument to a Clean function

Implement graph_to_string in WebAssembly and corresponding deserialize_from_prelinked_interpreter in native Clean

Closes #86

See merge request !118

Add copy_to_string to the WebAssembly runtime with jsSerializeOnClient in ABC.Interpreter.JavaScript

Add jsForceFetch (allows for returning a JSRef from JavaScript which may be copied later when forced; this is more efficient if the value does not always need to be copied)

Expose global from abc-interpreter.js to be able to add global JavaScript variables in node.js settings

JavaScript runtime: set ABC global variable in ap (the result may contain references to shared nodes, seen when using promises)