Cleanup and overhaul (#21)

* Syntax cleanup

* More minor cleanup, use Linq

* Fix broken features by using correct values

* Feature flags the same

* Features are modular

* No AlphaFS, more .NET versions

* Fix appveyor

* Put back identifiers, for some reason

* String interpolation, modernization

* Better use of GetField

* XmlTextWriter to remove possible issues

* Fix header for OpenMSX

SabreTools.Library/External/Compress/ZipFile/ZLib/Deflate.cs

@@ -157,14 +157,14 @@ namespace Compress.ZipFile.ZLib
         {
             "need dictionary",
             "stream end",
-            "",
+            string.Empty,
             "file error",
             "stream error",
             "data error",
             "insufficient memory",
             "buffer error",
             "incompatible version",
-            ""
+            string.Empty
         };
 
         // preset dictionary flag in zlib header