Add Office 2016 support, bump to v1.20

Office 2016 Standard, Professional Plus, and Home & Business editions
added with PerpetualVL2019 channel for volume licenses.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

InstaSoftOfficeTool.csproj

@@ -9,9 +9,9 @@
     <Company>InstaSoft Zrt.</Company>
     <Product>InstaSoft Office Tool</Product>
     <Copyright>Copyright (c) InstaSoft Zrt. 2026</Copyright>
-    <Version>1.1.9</Version>
-    <AssemblyVersion>1.1.9.0</AssemblyVersion>
-    <FileVersion>1.1.9.0</FileVersion>
+    <Version>1.20</Version>
+    <AssemblyVersion>1.20.0.0</AssemblyVersion>
+    <FileVersion>1.20.0.0</FileVersion>
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <LangVersion>latest</LangVersion>
   </PropertyGroup>