CB-8056 Implement splashscreen for Windows platform

The plugin implementation has been moved to the platform code
Documented SplashScreenBackgroundColor preference for Windows
Updated the docs
Updated plugin dependencies - cordova-windows@5 is required
Updated the plugin version to 4.0.0

www/windows/SplashScreenProxy.js

@@ -20,56 +20,15 @@
 */
 
 /*jslint sloppy:true */
-/*global WinJS */
 
-var cordova = require('cordova');
-
-var isPhone = (cordova.platformId == "windows") && WinJS.Utilities.isPhone;
-var isHosted = window.location.protocol.indexOf('http') === 0;
-var localSplash = null, localSplashImage = null;
-var bgColor = "#464646"; // default backgrond color; TDOO - read it from .appxmanifest
-var splashImageSrc = (isHosted ? "ms-appx-web" : "ms-appx") + ":///images/" +
-    (isPhone ? "splashscreenphone.png" : "splashscreen.png");
+var splash = require('cordova/splashscreen');
 
 var SplashScreen = {
-    setBGColor: function (cssBGColor) {
-        bgColor = cssBGColor;
-        if (localSplash) {
-            localSplash.style.backgroundColor = bgColor;
-        }
-    },
     show: function () {
-        if (localSplash) {
-            return; // already showed
-        }
-
-        localSplash = document.createElement("div");
-        localSplash.style.backgroundColor = bgColor;
-        localSplash.style.position = "fixed";
-        localSplash.style.top = "0";
-        localSplash.style.width = "100%";
-        localSplash.style.height = "100%";
-
-        localSplashImage = document.createElement("img");
-        localSplashImage.src = splashImageSrc;
-        localSplashImage.style.maxWidth = "100%";
-        localSplashImage.style.maxHeight = "100%";
-        // center horizontally
-        localSplashImage.style.margin = "0 auto";
-        localSplashImage.style.display = "block";
-        // center vertically
-        localSplashImage.style.position = "relative";
-        localSplashImage.style.top = "50%";
-        localSplashImage.style.transform = "translateY(-50%)";
-
-        localSplash.appendChild(localSplashImage);
-        document.body.appendChild(localSplash);
+        splash.show();
     },
     hide: function () {
-        if (localSplash) {
-            document.body.removeChild(localSplash);
-            localSplash = null;
-        }
+        splash.hide();
     }
 };