Changed functionality of getGrossValue and added getValue. Added and ...

...fixed documentation

@adamvoncorswant @mikaellothman 

Hope we didn't do duplicate work mikael, sorry if we did!

I think we need to call it net and not just value because there are a lot of functions named somethingValue.
Shouldn't it say "Rounds the value to a long using ..." instead of "without using" ?