Make more helper functions to navigate the component tree

[mitar]

So while there are functions to navigate one level of component tree, there should be also functions which navigate multiple levels, do it recursively. Imagine a jQuery selectors for selecting ancestor or descendant components.

The issue is that often you would want to find the first component matching some condition, not all of them. So it might be good to provide this as an iterator?

We should also document this and explain proposed use (finding by matching on some property and not number of levels, accessing components' state/public API). Explain that moving across data contexts is fragile and that better is to move between components and then call .data() on them (or any other state, reactive field).

[janat08]

So maybe static methods could be passed down to children automatically, and with them being aware of their parents, they could just invoke method within parent to whom method belongs.

PS read #82