[4.2] Ability to pass '0' as label to Form::label

Resolves the issue of not being able to make labels with the text being a zero.
`{{ Form::label("nps","0") }}`
The code improves on this by casting the value to a string and checking if it is an empty string or not when deciding between showing the actual value or generating a string from the field name.

Would this work for you?