Feature refactors with context aware view eagle

@michaelobriena 

I know this is annoying, but I wanted to take a deep dive into FlexibleLayout and see what came out. I think the pattern used in GridLayout and FlexibleLayout of creating lots of modifiers and a ViewSequence was overly complicated. The state of the layout was duplicated in several places (modifiers, state variables, and arrays) adding redundant complexity, instead of being a derivative of the core state (in the case of FlexibleLayout, it is the ratios). I'd like it if you could take a look at this PR and we can hash out a way forward tomorrow. This version isn't meant as a replacement, and some of the functionality is also missing (only direction_X is supported, for instance, and better logic should be included to add/remove nodes). But I'd like for this to frame a conversation moving forward. 

I'd also like to point out, there is a branch (fix-nonNumericTransitionable) of TweenTransition to support transitioning arrays with non-numeric values (e.g., [1, true] -> [2, true]), though non-numeric values themselves can't yet be transitioned, nor does physics supports this yet.