waterfall config fine-adjustments

* hide the waterfall colors input when pre-defined color scheme is
  selected
* skip unparseable lines on custom color input
* fallback to black and white if custom color config is unusable
* always use the waterfall classes when sending changes to the client

htdocs/settings.js

@@ -4,4 +4,5 @@ $(function(){
     $('.imageupload').imageUpload();
     $('.bookmarks').bookmarktable();
     $('.wsjt-decoding-depths').wsjtDecodingDepthsInput();
+    $('#waterfall_scheme').waterfallDropdown();
 });