Add opt.SetValue

Author: DavidGamba

user_options.go

@@ -185,6 +185,13 @@ func (gopt *GetOpt) Value(name string) interface{} {
 	return nil
 }
 
+func (gopt *GetOpt) SetValue(name string, value ...string) error {
+	if v, ok := gopt.programTree.ChildOptions[name]; ok {
+		return v.Save(value...)
+	}
+	panic("option not found")
+}
+
 // Bool - define a `bool` option and its aliases.
 // It returns a `*bool` pointing to the variable holding the result.
 // If the option is found, the result will be the opposite of the provided default.