Build: Prep for izpack 5.2.3 (Github i2p#86)

Update shortcut spec format, old format does not work with 5.2.3,
new format works with 4.3.0, 5.1.3, and 5.2.3

Format grabbed from ./izpack-dist/src/main/izpack/shortcutSpec.xml in izpack repo https://github.com/izpack/izpack
and specified at https://izpack.atlassian.net/wiki/spaces/IZPACK/pages/491733/Shortcut+Specification

installer/resources/shortcutSpec.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<shortcuts>
+<izpack:shortcuts version="5.0"
+                  xmlns:izpack="http://izpack.org/schema/shortcuts"
+                  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                  xsi:schemaLocation="http://izpack.org/schema/shortcuts http://izpack.org/schema/5.0/izpack-shortcuts-5.0.xsd">
+ <skipIfNotSupported/>
  <programGroup defaultName="I2P" location="startMenu" />
  <shortcut name="Open I2P Profile Folder (service)"
           target="explorer"
@@ -49,4 +53,4 @@
            startMenu="no"
            programGroup="yes"
            startup="no" />
-</shortcuts>
+</izpack:shortcuts>