Update app_env_variables.sample.rb to document SECRET_TOKEN parameter.
WIP on HAS theme: content and styles for nav bar

[#53913087] This gets the needed content in to the nav bar, hides it from the MW/default themes, and makes a first cut at formatting it for HAS.

https://www.pivotaltracker.com/story/show/53913087
Moves activity_nav partial from page to shared
rm old comment
Remove Lato for Helvetica in HAS themes
Shows the whole HAS/NGS nav menu for [#53913087].

There are some missing details, but the raw navigation menu is in place now.

https://www.pivotaltracker.com/story/show/53913087
Set up color variables for HAS-NGS style
Pretty close to a complete nav bar.

[#53913087] This provides the full drop-down "MENU" on the left of the HAS-NGS nav bar and fixes a few other design details.

https://www.pivotaltracker.com/story/show/53913087
Assets for HAS module themes, with backgrounds

This splits HAS into five themes, which share a common CSS file (has-styles.scss) but also have custom files which pull in different background images (and, eventually, different header graphics). This is most of [#53912853]

https://www.pivotaltracker.com/story/show/53912853
Themes haven't had footers for a few revisions
Migration to create five HAS themes

Just a quick way to create five themes without using a form [#53912853]

https://www.pivotaltracker.com/story/show/53912853