Perform some code refactor

api/src/main/kotlin/io/smnp/callable/function/Function.kt

@@ -10,10 +10,10 @@ abstract class Function(val name: String) {
     private var definitions: List<FunctionDefinition> = mutableListOf()
     private var _module: Module? = null
     var module: Module
-        get() = _module ?: throw RuntimeException("Method has not set module yet")
+        get() = _module ?: throw RuntimeException("Function has not set module yet")
         set(value) {
             if (_module != null) {
-                throw RuntimeException("Module of method is already set to ${module.canonicalName}")
+                throw RuntimeException("Function of method is already set to ${module.canonicalName}")
             }
             _module = value
         }

api/src/main/kotlin/io/smnp/ext/ModuleDefinition.kt

@@ -2,10 +2,12 @@ package io.smnp.ext
 
 import io.smnp.callable.function.Function
 import io.smnp.callable.method.Method
+import io.smnp.type.module.Module
 import org.pf4j.ExtensionPoint
 
-interface ModuleDefinition : ExtensionPoint {
-    fun modulePath(): String
-    fun functions(): List<Function>
-    fun methods(): List<Method>
+abstract class ModuleDefinition(val path: String) : ExtensionPoint {
+    open fun functions(): List<Function> = emptyList()
+    open fun methods(): List<Method> = emptyList()
+
+    fun module(): Module = Module.create(path, functions(), methods())
 }