map function for Double property

[b25rb2hkb25kbw]

Currently, if I want to map DoubleProperty to String, I cannot use map function directly like:

Easybind.map(someDoubleProperty, someMapperFromDoubleToString)

because DoubleProperty only implements ObservableValue<Number>, not ObservableValue<Double> and thus the second argument should be Function<Number, U>. I think it would be better the method is overloaded for arguments (ObservableDoubleValue, DoubleFunction), (ObservableIntValue, IntFunction) and so on.

It seems that this repository is not maintained these days. Since this is really splendid project, I hope that it will be continued developing...