History for Creating Custom Viewers

Maria Nattestad 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for dx commands, but shortened the output from dx ls -al for the Viewers project, since this would be immediately outdated when we update Viewers.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. [b97d1e7]