Updated Input and Navs doc

I updated the doc about the Input to reflect that you can now use any renderable component as the addon.

And I updated the Navs doc to be closer to bootstrap doc. So i added dropdown/stacked/justified examples.

I'll try to updated some other parts of the doc if I have some free time!
Would be good to split these examples out and put the simpler `pills` example first. Its nice to have simple copy paste-able code for the basic examples.