Add basic/generic Buefy support to the Form class

mostly just affects rendering, apparently backend logic needn't really change?

tailbone/templates/reports/generate.mako

@@ -16,7 +16,7 @@
 
   <div class="form-wrapper">
     <p style="padding: 1em;">${report.__doc__}</p>
-    ${form.render(template='/forms/form{}.mako'.format('_buefy' if use_buefy else ''))|n}
+    ${form.render()|n}
   </div><!-- form-wrapper -->
 
   <ul id="context-menu">