some fixes and more user friendly form to buy instantplan

rowers/templates/instantplan.html

@@ -33,6 +33,7 @@
     <p>Price: {{ plan.price }}&euro;</p>
     {% endif %}
   </li>
+  {% if form %}
   <li class="grid_2">
     <p>
       When you submit this form, a training plan will be created based on {{ plan.name }}, ending at your target date,
@@ -58,6 +59,13 @@
     {% endif %}
     </form>
   </li>
+  {% else %}
+  <li class="grid_2">
+    <p>
+      <a href="/login/?next={{ request.get_full_path }}">Log in</a> to install this plan to your training calendar.
+    </p>
+  </li>
+  {% endif %}
   <li class="grid_4">
     <h1>Plan Details</h1>
     <table width="100%" class="listtable shortpadded">