SCRATCH separate the generic updater logic from the application

tests/data/tst_DownloadTask-test_writeInstallScript.xml

@@ -0,0 +1,17 @@
+<update version="3">
+ <install>
+  <file>
+   <source>sourceOne</source>
+   <dest>destOne</dest>
+   <mode>0777</mode>
+  </file>
+  <file>
+   <source>MultiMC.exe</source>
+   <dest>M/u/l/t/i/M/C/e/x/e</dest>
+   <mode>0644</mode>
+  </file>
+ </install>
+ <uninstall>
+  <file>toDelete.abc</file>
+ </uninstall>
+</update>