Add authentication and the basis of the browser module.

A user authentication module based on flask-security is added, which
allows users to login and change/recover passwords etc. Custom templates
are included for the user/password UIs.

A new setup script will initialise the user (and later settings) DB,
adding the first user and granting them an Administrator role.

A redirects blueprint module is added to handle simple URL redirects.

A browser module is added and currently renders a skeleton page with
a menu bar, gravatar and jumbotron.

NOTE FOR LATER: Currently this code might make the nice basis for any
web app that needs user management and plugins. Hmmm....

web/pgadmin/templates/security/fields.html

@@ -0,0 +1,10 @@
+{% macro render_field_with_errors(field, type) %}
+<div class="form-group{% if field.errors %} has-error{% endif %}">
+  <input class="form-control" placeholder="{{ field.label.text }}" name="{{ field.name }}" type="{{ type }}">
+</div>
+{% if field.errors %}
+{% for error in field.errors %}
+<span class="help-block">{{ error }}</span>
+{% endfor %}
+{% endif %}
+{% endmacro %}