[C#] Exclude generated sources.

Author: vyazelenko

.gitignore

@@ -85,18 +85,8 @@ csharp/*/bin
 csharp/*/obj
 csharp/.vs
 csharp/TestResults
-csharp/sbe-generated/baseline
-csharp/sbe-generated/baseline-bigendian
-csharp/sbe-generated/extension
-csharp/sbe-generated/issue435
-csharp/sbe-generated/issue483
-csharp/sbe-generated/issue560
-csharp/sbe-generated/issue661
-csharp/sbe-generated/since-deprecated
-csharp/sbe-generated/order_check
-csharp/sbe-generated/mktdata/*.cs
-csharp/sbe-generated/uk_co_real_logic_sbe_benchmarks_fix
-csharp/sbe-generated/test_message_schema
+csharp/sbe-generated/
+!csharp/sbe-generated/sbe-generated.csproj
 csharp/sbe-tests/*.sbe
 csharp/nuget/
 csharp/csharp.sln.DotSettings.user