More page formatting

Added server-side logic for register.html validation
Keep form firelds on register.html in the event of wrong input fields to save users from retyping info
More button rounding

powerdnsadmin/templates/admin_history_table.html

@@ -6,7 +6,7 @@
   </p>
 {% endif %}
 
-<div class="box-body"></div>
+<div class="card-body"></div>
   <table id="tbl_history" class="table table-bordered table-striped">
     <thead>
       <tr>