September 12, 2017:
Add Creating-Custom-Viewers page (#200)
* Add creating custom viewers developer tutorial
* Format creating-custom-viewers page
* Add link to custom-visualizers from UI/Visualize
* Format creating-custom-viewers
* Cleaned up pages (#201)
* Cleaned up Visualize page
* Fixed line widths; cleaned up some wordier sentences; modified some code blocks
* Minor text fix
* Add output for dx commands and fix Viewers ID
Added output for dx commands, but shortened the output from dx ls -al for the Viewers project, since this would be immediately outdated when we update Viewers.
Note that the public Viewers project has a specific project ID (project-BQ7k4pj0FVky4kVkgVf0000F) that should not be listed as project-xxxx in code blocks. This project is hard-coded in the platform to show up in the visualize tab, so this is the permanent place that developers can download Viewer examples.