NIF, NIE and CIF validation numbers:

* 'n' variable changed to 'controlDigit'.
* Fixed some code styling: spaces after comas, and spaces before curly braces.
* Removed NIF, NIE and CIF variables with value = value.toUpperCase().
* Inlined just one use variables (cadenadni, and some others).
* Removed unused variables.
* Some substring() replaced with charAt().
* Comments translated to English.