host and file handling changes

- track files in the database
- track file content in the database
- hosts are no longer a "top-level" object, and are now only
  unique per-playbook
- cli changes to support the above
- limited web ui support for the above
- as part of the changes w/r/t host handling, host facts are known
  displayed in the `/host/<hostid>` view.

We will be addressing the following in a future commit:

- Providing better host browsing for each ansible run (note that right
  now you can get to the host page by selecting a hostname from a task
  list)

- Providing links to view file contents in the web ui

This was originally https://github.com/dmsimard/ara/pull/105

Change-Id: Iba7e62c911526a5e2c351e407aed4118ddd1afaf

ara/templates/navbar.html

@@ -11,16 +11,6 @@
     </div>
     <div class="navbar-collapse collapse">
       <ul class="nav navbar-nav">
-        <li class="dropdown">
-          <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Hosts <span class="caret"></span></a>
-          <ul class="dropdown-menu">
-            {% for host in hosts %}
-            <li><a href="{{ url_for('host.show_host', host=host.name) }}">{{ host.name }}</a></li>
-            {% endfor %}
-            <li><a href="{{ url_for('host.host_summary') }}">All hosts...</a></li>
-          </ul>
-        </li>
-
         <li class="dropdown">
           <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Playbooks <span class="caret"></span></a>
           <ul class="dropdown-menu">