Custom label and value multiple field
Using Field Collection module must serve your purpose. 

After installing the module, create a field collection with two text fields - label and value.

Now attach this field collection to a content type and set its value to unlimited.

in essence what you will have is: 
 1. When the form loads, you have two fields, a label and a value
 2. An add more button, which when clicked will generate another set of label value pair.

Hope this helps.