Fix possible thread leak in PN when recompiled

Bug affected the Persistence Network when it was configured to use a file data source (yml, json, ini, csv, xml). If a recompile is followed by garbage collection, a thread leak may occur. Setting corePoolSize to zero allows the thread to timeout, and ultimately the whole pool to be garbage collected.

src/main/java/com/laytonsmith/persistence/io/ReadWriteFileConnection.java

@@ -76,7 +76,7 @@ public ReadWriteFileConnection(URI uri, File workingDirectory, String blankDataM
 			reader.getTopLevelFile().createNewFile();
 		}
 		this.blankDataModel = blankDataModel;
-		this.service = new ThreadPoolExecutor(1, 1,
+		this.service = new ThreadPoolExecutor(0, 1,
 				60L, TimeUnit.MILLISECONDS,
 				new LinkedBlockingQueue<Runnable>(),
 				new ThreadFactory() {