Bump version to v3.3.1

Change-Id: Ia0f3aa3783bf85893ae35c17f9005043a005a5f0
diff --git a/build.gradle b/build.gradle
index 3d26af9..2b950b2 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,4 +5,4 @@
 }
 
 // Zentrale Projektversion für korapxmltool
-version = '3.3.0'
+version = '3.3.1'