Bind many more properties to scripts

Notable potentially breaking changes:
- PROPERTY_USAGE_NOEDITOR is now PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_NETWORK, without PROPERTY_USAGE_INTERNAL
- Some properties were renamed, and sometimes even shadowed by new ones
- New getter methods (some virtual) were added

core/script_language.cpp

@@ -61,6 +61,8 @@ void Script::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("has_script_signal", "signal_name"), &Script::has_script_signal);
 
 	ClassDB::bind_method(D_METHOD("is_tool"), &Script::is_tool);
+
+	ADD_PROPERTY(PropertyInfo(Variant::STRING, "source_code", PROPERTY_HINT_NONE, "", 0), "set_source_code", "get_source_code");
 }
 
 void ScriptServer::set_scripting_enabled(bool p_enabled) {