Improve paged demo

[Krumuvecis]

Regarding paged demo

Menu

• common header with buttons for 3 menu pages. buttons:
  • starting page
  • settings page
  • demo select page

General improvements

• for pages:
  • common header for non-menu pages
  • Side panels for page-specific info and buttons
  • simple animation in middle
• use demo-specific data
• FileHandler adapter tests