Bump version to v2.99

Change-Id: I457af9560bcf1e761fdf5d2dca63b6d827ac2324
diff --git a/build.gradle b/build.gradle
index 55172cb..9c4f3d0 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,4 +5,4 @@
 }
 
 // Zentrale Projektversion für korapxmltool
-version = '2.20'
+version = '2.99'