Admin dashboard route and page

[kasugaijin]

Describe your change in plain English.

This PR:

• adds route to dashboard
• adds dashboard controller
• adds index view file with start of the navbar for dashboard UI

Note that

• once we are happy with the basic navbar options, will need to update classes to get functionality working properly
• some discussion (at least for my benefit) on how we want to organize view templates for this portion of the site as I am thinking we want a SPA feel here.

[edwinthinks]

When we get to work on this page let's make sure to use https://github.com/comfy/active_link_to which makes things a bit easier to show active states on links.

[kasugaijin]

Yes the hrefs in there right now are dropped in from the template. All need replacing.

[kasugaijin]

I updated to use a dashboard layout template that renders the navbar and whatever template is required depending on the selection from the navbar using yield.

I think all we have to do is set up other templates, named and routed appropriately, and add below and it will work with the render

<% content_for :dashboard_content do %>
  <!-- Content for Dashboard link goes here -->
<% end %>

[kasugaijin]

FYI: I made this PR yesterday as a little launch pad for Jade to continue on with. As such, there's a few things that are incomplete with the intent they will be continue. I guess Jade could contribute to this branch if we don't want to merge it in. I am open.