Added support for BigDecimal and BigInteger

Hello, in our projects we use `BigDecimal` for decimal numbers. These are not supported by your component, but adding support was easy.

You used reflection to call static `valueOf` method of some number classes. Because `BigDecimal` does not have this method, but instead it has a `String` constructor, I decided to remove the reflection and instead added the `parseNumberValue()` method, which parses all classes. I also fixed parsing for primitive `byte` and `short`, which were ommited in the `getProperNumericClass()` method (now removed). `BigInteger` was added as well.

Please review my changes and I'd be glad if you merge it to your branch. Thank you for the great work!

Viliam