HER-1547 some sites may require an 'Accept' header

* FetchHTTP.java
    "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
    by default - this is what my firefox 4.0 for mac sends
* profile-crawler-beans.cxml
    commented-out default value

engine/src/main/resources/org/archive/crawler/restlet/profile-crawler-beans.cxml

@@ -269,6 +269,7 @@ http://example.example/example
   <!-- <property name="sslTrustLevel" value="OPEN" /> -->
   <!-- <property name="acceptHeaders"> 
         <list>
+         <value>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8</value>
         </list>
        </property>
   -->

modules/src/main/java/org/archive/modules/fetcher/FetchHTTP.java

@@ -42,9 +42,9 @@ import java.security.KeyManagementException;
 import java.security.KeyStoreException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -195,11 +195,13 @@ public class FetchHTTP extends Processor implements Lifecycle {
 
     /**
      * Accept Headers to include in each request. Each must be the complete
-     * header, e.g., 'Accept-Language: en'. (Thus, this can also be used to 
-     * other headers not beginning 'Accept-' as well.)
+     * header, e.g., 'Accept-Language: en'. (Thus, this can also be used to
+     * other headers not beginning 'Accept-' as well.) By default heritrix sends
+     * an Accept header similar to what a typical browser would send (the value
+     * comes from Firefox 4.0).
      */
     {
-        setAcceptHeaders(new LinkedList<String>());
+        setAcceptHeaders(Arrays.asList("Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"));
     }
     @SuppressWarnings("unchecked")
     public List<String> getAcceptHeaders() {