Wire example

I have prepared example of use [Wire](https://pub.dev/packages/wire) library for state management and separation of concerns, another way of Flux implementation, it's almost complete clone (except on line in model) and reuse of the business logic from example of Wire use in [original repository](https://github.com/DQvsRA/Wire/tree/master/example/todo) - web version with template from TodoMVC. Also this example use Flutter Widget for Wire - [WireDataBuilder](https://pub.dev/packages/wire_flutter).
The library is still in developing, but I think major API and concepts won't change, I have plan to add "middleware" and "traces" to inspect current state and registered wires/signals and data.
@brianegan could you please check my PR from wire branch?

Start by comparing the repository's existing Flutter architecture samples with the Wire example and its linked original TodoMVC implementation. Review the proposed wire-branch example for the described state-management and business-logic reuse; the issue is done when the example is reviewed and accepted.

Written by the indexing model from the issue text.