Change BudgetInvestmentStatus to Milestone::Status

Generalize the BudgetInvestmentStatus model to Milestone::Status so it
is not specific to budget investments, but can be used for any entity
which has milestones. This is in preparation to make the Milestone
model polymorphic and usable by entities other than budget investments.

app/views/admin/milestone_statuses/_form.html.erb

@@ -0,0 +1,10 @@
+<%= form_for [:admin, @status] do |f| %>
+  <%= render 'shared/errors', resource: @status %>
+
+  <%= f.text_field :name %>
+  <%= f.text_area :description %>
+
+  <div class="margin-top">
+    <%= f.submit class: "button success" %>
+  </div>
+<% end %>

app/views/admin/milestone_statuses/edit.html.erb

@@ -0,0 +1,5 @@
+<%= back_link_to admin_milestone_statuses_path %>
+
+<h2><%= t("admin.statuses.edit.title") %></h2>
+
+<%= render '/admin/milestone_statuses/form' %>

app/views/admin/milestone_statuses/index.html.erb

@@ -0,0 +1,41 @@
+<h2 class="inline-block"><%= t("admin.statuses.index.title") %></h2>
+
+<%= link_to t("admin.statuses.index.new_status"),
+            new_admin_milestone_status_path,
+            class: "button float-right margin-right" %>
+
+<% if @statuses.any? %>
+  <table>
+    <thead>
+      <tr>
+        <th><%= t("admin.statuses.index.table_name") %></th>
+        <th><%= t("admin.statuses.index.table_description") %></th>
+        <th><%= t("admin.statuses.index.table_actions") %></th>
+      </tr>
+    </thead>
+    <tbody>
+      <% @statuses.each do |status| %>
+        <tr id="<%= dom_id(status) %>" class="milestone_status">
+          <td>
+            <%= status.name %>
+          </td>
+          <td>
+            <%= status.description %>
+          </td>
+          <td>
+            <%= link_to t("admin.statuses.index.edit"),
+                        edit_admin_milestone_status_path(status),
+                        method: :get, class: "button hollow" %>
+            <%= link_to t("admin.statuses.index.delete"),
+                        admin_milestone_status_path(status),
+                        method: :delete, class: "button hollow alert" %>
+          </td>
+        </tr>
+      <% end %>
+    </tbody>
+  </table>
+<% else %>
+  <div data-alert class="callout primary margin-top clear">
+    <%= t("admin.statuses.index.empty_statuses") %>
+  </div>
+<% end %>

app/views/admin/milestone_statuses/new.html.erb

@@ -0,0 +1,5 @@
+<%= back_link_to admin_milestone_statuses_path %>
+
+<h2><%= t("admin.statuses.new.title") %></h2>
+
+<%= render '/admin/milestone_statuses/form' %>