HER-1467 Allow periodic checkpointing and checkpoint-copy-logs to be set/unset during crawl

* CheckpointService.java
    reorganize so that checkpoint timedTask is reset whenever interval is reset on a running crawl
* CheckpointSuccessEvent.java, CrawlJob.java
    report successes as new kind of ApplicationEvent; propagagte to job log
* BdbModule.java
    remove obsolete unconsulted checkpointCopyLogs setting

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

@@ -172,14 +172,6 @@ public class BdbModule implements Lifecycle, Checkpointable, Closeable {
         this.useSharedCache = useSharedCache;
     }
     
-    boolean checkpointCopyLogs = true; 
-    public boolean getCheckpointCopyLogs() {
-        return checkpointCopyLogs;
-    }
-    public void setCheckpointCopyLogs(boolean checkpointCopyLogs) {
-        this.checkpointCopyLogs = checkpointCopyLogs;
-    }
-    
     /**
      * Expected number of concurrent threads; used to tune nLockTables
      * according to JE FAQ