* Move site title helper to instance helper (name change only)

* Remove newline in <title> tag

* Add site_hostname helper method to wrap up local_domain value

* Use site_hostname helper in places that need local_domain value

* Basic onboarding modal that's shown to users once

* Lay out pages 2 through 5, add images, style modals (#1509)

* Lay out pages 2 through 5

Added images and laid out pages 2 through 5 in the jsx file. SCSS will
come, still working on just seeing if this works at all.

* Fix jsx errors, add images to modal pages, style modal pages

* Add animations to onboarding pager changes, improve wording and styling

* Finishing touches on the onboarding

* Add missing propTypes

* Update wording

to only those from local users; Add link to "extended information" to
getting started in the UI; Add defaults for posting privacy; Change
how publish button looks depending on posting privacy chosen