Add numerical attribute types

[zhedar]

Currently there's only Integer as a numeric Attributetype. What about adding other types like Double or Number? The latter would be quite nice, because the user could provide any type, even BigDecimal oder BigInteger and the component would still be able to process it without any drawbacks.

[stephanrauh]

Currently, I don't see the use case. So far, every numeric attribute of our components was an integer. I'm not opposed to your proposal - but I don't see a point in implementing it prematurely.