Part of [HER-1836] let more than one extractor run on a single url - new

setting "independentExtractors" - when enabled, extractors run regardless of
whether other extractors have run
* profile-crawler-beans.cxml, AbstractFrontier.java, ExtractorParameters.java,
  Extractor.java
    new setting independentExtractors
* ContentExtractor.java
    shouldProcess() - respect independentExtractors

engine/src/main/java/org/archive/crawler/frontier/AbstractFrontier.java

@@ -145,6 +145,15 @@ public abstract class AbstractFrontier
         kp.put("maxOutlinks", max);
     }
     
+    {
+        setIndependentExtractors(false);
+    }
+    public boolean isIndependentExtractors() {
+        return (Boolean) kp.get("independentExtractors");
+    }
+    public void setIndependentExtractors(boolean enabled) {
+        kp.put("independentExtractors", enabled);
+    }
     
     /** inbound updates: URIs to be scheduled, finished; requested state changes */
     protected BlockingQueue<InEvent> inbound;