Implemented serializable doc bits vector for caching on disk.

Change-Id: I5ffdbe429b68b71d165c3ecf5b7504ac01a9a1ec
diff --git a/src/test/resources/ehcache.xml b/src/test/resources/ehcache.xml
new file mode 100644
index 0000000..b293534
--- /dev/null
+++ b/src/test/resources/ehcache.xml
@@ -0,0 +1,22 @@
+<ehcache xsi:noNamespaceSchemaLocation="http://www.ehcache.org/ehcache.xsd"
+	updateCheck="true" monitoring="autodetect" dynamicConfig="true">
+
+	<diskStore path="./krill_cache" />
+
+	<defaultCache 
+		maxEntriesLocalHeap="0" 
+		eternal="false"
+		timeToIdleSeconds="1200" 
+		timeToLiveSeconds="1200">
+	</defaultCache>
+
+	<cache name="named_vc" 
+		eternal="true" 
+		memoryStoreEvictionPolicy="LRU"
+		maxElementsInMemory="1" 
+		maxBytesLocalDisk="1G"
+		diskExpiryThreadIntervalSeconds = "120" > 
+		<persistence strategy="localTempSwap"/>
+	</cache>
+
+</ehcache>
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