Make Bloom size configurable without system properties

* BloomUriUniqFilter.java
    make bloom size configurable via bean properties
    change implementing class to BloomFilter64bit (given growing prevalance of 64bit JVMs and larger heaps)
* BloomUriUniqFilterTest.java
    update test for property-set sizing
* BloomFilter64bit.java
    improve comment

engine/src/test/java/org/archive/crawler/util/BloomUriUniqFilterTest.java

@@ -52,7 +52,10 @@ implements UriUniqFilter.CrawlUriReceiver {
 
     protected void setUp() throws Exception {
         super.setUp();
-        this.filter = new BloomUriUniqFilter(2000,24);
+        this.filter = new BloomUriUniqFilter();
+        this.filter.setExpectedInserts(2000);
+        this.filter.setHashCount(24); 
+        this.filter.afterPropertiesSet();
         this.filter.setDestination(this);
     }