Restore Buy bitcoin page and add buy.bitcoin.com as a service there

src/js/controllers/buyBitcoindotcom.js

@@ -0,0 +1,16 @@
+'use strict';
+
+angular.module('copayApp.controllers').controller('buyBitcoindotcomController',
+  function($scope, $timeout, $ionicModal, $log, $state, $ionicHistory, lodash, bitcoincomService, externalLinkService, popupService) {
+
+    $scope.openExternalLink = function(url) {
+      externalLinkService.open(url);
+    };
+
+    var buyBitcoindotcom = function() {
+    };
+
+    $scope.$on("$ionicView.beforeEnter", function(event, data) {
+      buyBitcoindotcom();
+    });
+  });