Create settings page placeholder, add auth pattern

This adds a pattern for creating pages that require authentication. The
settings page is currently empty, but it's helpful to figure out how to
do this pattern.

templates/empty-auth.html

@@ -0,0 +1,7 @@
+{{template "authenticated.html" .}}
+
+{{define "title"}}Dash{{end}}
+{{define "style"}}
+{{end}}
+{{define "content"}}
+{{end}}