Move to Handlebars.js from Mustache.js

Scott, Bill? Which one of you wants to merge this?

Tested locally, appears functional. Another test or testing in the APK would be great.

Move templating to use Handlebars.js instead of Mustache.js, remove
Mustache.js code and references.

Signed-off-by: Jeff Godin <jgodin@tadl.org>