New UI control to toggle signposts on/off based on their content.

Pretty substantial javascript refactoring:
 * All javascript is now in funtions.js.  There is no javascript at all
   in index.html
 * Configuration options moved from template.html to config.js
   template.html moved to web_assets/index.html

config.js allows you to specify pattern-label pairs.  Each label will be
added to an on-screen "signposts" control.  Clicking the checkbox by
each label will show/hide any signposts that match the pattern attached
to that label.  config.js has some examples.

TODO:
 * The signposts control needs better styling.
 * The new javascript needs testing in IE.  Seems ok in Chome and FF.

These large changes may be hard to merge if you have non-trivial JS
changes to template.html locally.  Apologies in advance

config.js

@@ -0,0 +1,28 @@
+
+  var config = {
+    path:        'tiles',
+    fileExt:     '{imgformat}',
+    tileSize:     384,
+    defaultZoom:  1,
+    maxZoom:      {maxzoom},
+    cacheMinutes: 0, // Change this to have browsers automatically request new images every x minutes
+    debug:        false
+  };
+
+
+// define a list of pattern-label pairs.  Each label will appear
+// in the 'Signposts' control, allowing your users to quickly enable
+// or disable certain labels.  See below for some examples:
+var signGroups = {
+//    "Directions": /^#Direction/i,
+//    "Big Dig": /big\s*dig/i,
+//    "Warnings": /warning/i,
+};
+
+// Please leave the following variables here:
+var markerCollection = {}; // holds groups of markers
+
+var map;
+
+var markersInit = false;
+var regionsInit = false;