Functions documentation updates

All Functions pages that have headings now have up-to-date "return values" specified. I went through all of them in the C++ source code to check exactly what's returned 

Any that have an <error> value should be wrapped in "try .. catch" clauses to avoid your script borking if Warzone throws an error. If you're not familiar with Error objects, check out MDN as they have lots of good documentation and examples.