Merge branch 'zulip' into 'master'

initial zulip.xml using IFS

See merge request !10

packages/zulip.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<packages>
+  <package id="zulip" name="Zulip Desktop App" revision="%version%.1" priority="0" reboot="false">
+  <variable name="version" value="4.0.0.0" />
+  <variable name="fileversion" value="4.0.0" />
+
+  <check type="file" condition="versiongreaterorequal" value="%version%" path="%PROGRAMFILES%\zulip\%fileversion%\Zulip.exe" />
+
+  <install cmd='%WPKGSOFTWARE%\wpkg\tools\7zip\7za.exe x -o"%PROGRAMFILES%\Zulip\%fileversion%" %WPKGSOFTWARE%\zulip\zulip-%fileversion%-x64.nsis.7z' />
+  <install cmd='cmd /c xcopy /sechky "%WPKGSOFTWARE%\zulip\global_config.json" "%PROGRAMFILES%\Zulip-Desktop-Config\" '/>
+  <install cmd='cscript %WPKGSOFTWARE%\wpkg\tools\create-shortcut.js /folder:"Zulip" /linkname:"Zulip %fileversion%" /target:"%PROGRAMFILES%\Zulip\%fileversion%\Zulip.exe"' />
+
+  <upgrade include='remove' />
+  <upgrade include='install' />
+
+  <remove cmd="taskkill /F /IM Zulip.exe">
+  <exit code="0" />
+  <exit code="128" />
+  </remove>
+  <remove cmd='cmd /c rmdir /s /q "%PROGRAMFILES%\Zulip"' />
+  <remove cmd='cmd /c rmdir /s /q "%PROGRAMFILES%\Zulip-Desktop-Config"' />
+  <remove cmd='cscript %WPKGSOFTWARE%\wpkg\tools\delete-shortcut.js /folder:"Zulip" ' />
+
+</package>
+</packages>