Add getter with out params

[signorpipo]

This left out materials getter and also index data getters which are a bit more complex

[DavidPeicho]

Please modify all original getters to re-use getX(), so that we don't duplicate code especially if we have an issue somewhere.

[DavidPeicho]

@SignorPipo I shouldn't have asked you to modify get/set extent actually, for backward compatibility, we need them exactly like before without using getExtents. People might be using them like that:

component.extents[0] = 1;

And that's not going to work with getExtents

[DavidPeicho]

Merci for this contribution!