Added simple PHP type hinting support to grammar for functions and class methods

- Only 'array' type is supported for now
Added support for namespaced and unnamespaced PHP class type hinting to grammar
Added support for type hinting for static PHP class methods to grammar
Added initial support for PHP function and instance/static class method argument type hinting to interpreter

- No enforcement is performed yet
Added PHP strict equality/inequality operators' support to README
Added partial PHP type hinting support to README
Added recent OOP features to README