Perform mass cleanup

This is cleanup based on both new .NET functionality (in 6 and 7) as well as a ton of simplifications and things that were missed that were caught due to the cleanup.

SabreTools.IO/Readers/IniReader.cs

@@ -105,7 +105,7 @@ namespace SabreTools.IO.Readers
             }
 
             // KeyValuePair
-            else if (CurrentLine.Contains("="))
+            else if (CurrentLine.Contains('='))
             {
                 // Split the line by '=' for key-value pairs
                 string[] data = CurrentLine.Split('=');