Feature/#95 deepclone (#101)

* rename method Clone to Copy

* added Cloneable interface

* added Value to Cloneable interface

* implemented Cloneable intefrace by array

* implemented Cloneable interface by Object

* unit tests for Object.Clone

* move core.IsCloneable to value.go

* change Clone function

* move IsClonable to package values

pkg/runtime/core/cloneable.go

@@ -0,0 +1,6 @@
+package core
+
+type Cloneable interface {
+	Value
+	Clone() Cloneable
+}