Add a "Back" button to the guided_registration stages

"Next" is green, indicating that it's the default path, the way
forward. "Back" is available but blue.

For extra consistency, the initial "Get ticket" button is now also a btn-success

pinaxcon/templates/dashboard.html

@@ -43,7 +43,7 @@
             </div>
             <div class="panel-body">
               <p>To attend the conference, you must register an attendee profile and purchase your ticket</p>
-              <a class="btn btn-lg btn-primary" role="button" href="{% url "guided_registration" %}">Get your ticket</a>
+              <a class="btn btn-lg btn-success" role="button" href="{% url "guided_registration" %}">Get your ticket</a>
             </div>
           </div>
         {% else %}

pinaxcon/templates/registrasion/guided_registration.html

@@ -45,7 +45,10 @@
     {% endfor %}
 
     <div class="btn-group">
-      <input class="btn btn-primary" type="submit" value="Next Step" />
+      {% if current_step > 1 %}
+      <a class="btn btn-primary" role="button" href="{{ previous_step }}">Back</a>
+      {% endif %}
+      <input class="btn btn-success" type="submit" value="Next Step" />
     </div>
   </form>
 

vendor/registrasion/registrasion/views.py

@@ -94,6 +94,7 @@ def guided_registration(request, page_number=None):
             with the following data::
 
                 {
+                    "previous_step": int(),  # Previous step
                     "current_step": int(),  # The current step in the
                                             # registration
                     "sections": sections,   # A list of
@@ -152,6 +153,8 @@ def guided_registration(request, page_number=None):
 
     page_number = int(page_number)
 
+    prev_step = page_number - 1
+
     next_step = redirect("guided_registration", page_number + 1)
 
     with BatchController.batch(request.user):
@@ -206,6 +209,7 @@ def guided_registration(request, page_number=None):
                 return next_step
 
     data = {
+        "previous_step": prev_step,
         "current_step": page_number,
         "sections": sections,
         "title": title,