Add trace plot options

Rename intermediate options
Add help page

A static page that explains some terminology
Add arrival time
Add Navigation to Help

Allows visitors to go back to stations list/map
Add view for help

This allows links like {% url 'status_display.views.help' %}
Fix typo
Add links to Help page on station(s) templates
Add inactive statusball when no station is selected
Merge branch 'help'

This adds a Help page to the public database
This page explains some terms and graphs used on other pages