[HER-1607] handle persist state when crawl starts up

* PersistProcessor.java, PersistLoadProcessor.java
    port [HER-1586] preloadSource setting/refactoring to H3
* IoUtils.java
    (getBufferedReader) utility method
* BdbModule.java
    explicit passthrough of settable deferredWrite property

commons/src/main/java/org/archive/bdb/BdbModule.java

@@ -102,7 +102,7 @@ Serializable, Closeable {
         boolean allowCreate;
         boolean sortedDuplicates;
         boolean transactional;
-
+        boolean deferredWrite = true; 
 
         public BdbConfig() {
         }
@@ -129,7 +129,7 @@ Serializable, Closeable {
 
         public DatabaseConfig toDatabaseConfig() {
             DatabaseConfig result = new DatabaseConfig();
-            result.setDeferredWrite(true);
+            result.setDeferredWrite(deferredWrite);
             result.setTransactional(transactional);
             result.setAllowCreate(allowCreate);
             result.setSortedDuplicates(sortedDuplicates);
@@ -145,6 +145,11 @@ Serializable, Closeable {
         public void setTransactional(boolean transactional) {
             this.transactional = transactional;
         }
+
+
+        public void setDeferredWrite(boolean b) {
+            this.deferredWrite = true; 
+        }
     }