java_gen: bump version to 0.3.5-SNAPSHOT

due to OFChecksum128 -> U128 rename in commit 7c15b1725 .
diff --git a/java_gen/pre-written/pom.xml b/java_gen/pre-written/pom.xml
index b4e81cc..e1c0630 100644
--- a/java_gen/pre-written/pom.xml
+++ b/java_gen/pre-written/pom.xml
@@ -10,7 +10,7 @@
 
     <groupId>org.projectfloodlight</groupId>
     <artifactId>openflowj</artifactId>
-    <version>0.3.4-SNAPSHOT</version>
+    <version>0.3.5-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>OpenFlowJ-Loxi</name>