Streamline Pages in Explorer

[Orasund]

Description

This PR is about a more streamline Page Example (The Button Page in particular).

I have few problems, that I like to fix:

• [x] rename Pages into Page (following the Elm convention for naming files)
• [x] Rework of UIExplorer.Tile
  • [x] Intro should not be wrapped in a card.
  • [x] Use Widget.Item for cards, in particular, add titles to cards.
• [x] Fixed up Themes
• [x] Rework of UIExplorer.Story
• [x] Capitalization of any text
• [x] Remove anything that is not needed (leftovers from the rewrite)
• [x] Add Type Signatures
• [x] Helper Functions for
  • [x] Options
  • [x] Views
  • [x] Demo
• [x] Remove Redundancies.
• [x] Add Documentation describing how to set up a new Page

Pull request solving issue #57.