Refactor Value and EvaluatorOutput models in order to get rid of optionals(?)

modules/io/src/main/kotlin/io/smnp/ext/io/function/PrintlnFunction.kt

@@ -9,7 +9,7 @@ import io.smnp.type.model.Value
 class PrintlnFunction : Function("println") {
     override fun define(new: FunctionDefinitionTool) {
         new function vararg(allTypes()) body { _,  (vararg) ->
-            println((vararg.value!! as List<Value>).joinToString("") { it.stringify() })
+            println((vararg.value as List<Value>).joinToString("") { it.stringify() })
             Value.void()
         }
     }

modules/io/src/main/kotlin/io/smnp/ext/io/function/ReadFunction.kt

@@ -11,7 +11,7 @@ import io.smnp.type.model.Value
 class ReadFunction : Function("read") {
    override fun define(new: FunctionDefinitionTool) {
       new function simple(optional(ofType(STRING))) body { _, arguments ->
-         arguments.getOrNull(0)?.let { print(it.value!!) }
+         arguments.getOrNull(0)?.let { print(it.value) }
          Value.string(readLine() ?: "")
       }
    }