Extract ViewNavigation component

[onlined]

Description

Three files use same navigation structure, so I extracted it to a
component for DRY.

Motivation and Context

• DRY
• Abstracting out implementation details

Checklist

[x] I have not included any built dist files (us maintainers do that prior to a new release)
[ ] I have added tests covering my changes
[x] All new and existing tests pass
[ ] My changes required the documentation to be updated
  [ ] I have updated the documentation accordingly
  [ ] I have updated the TypeScript 1.8 type definitions accordingly
  [ ] I have updated the TypeScript 2.0+ type definitions accordingly

[arqex]

This PR is great and it's definitely going in the right direction! If we are going to create smaller files, we probably would like to also update the folder structure.

I was thinking about something like:

src/
|-- DateTime.js
|-- parts/
|   |-- DateInput.js
|   |-- ViewNavigation.js
|-- playground/
|   |-- App.js
|   |-- index.js
|-- views/
|   |-- DaysView.js
|   |-- MonthsView.js
|   |-- YearsView.js

With the playground we have the problem to make it work after moving their files out from the root of /src.
What do you think?

[onlined]

@arqex Directory structure seems good, but I think it should be organized in another PR.