adding missing registrations in kryo

some classes were missing registration in kryo which causes less efficient serialization
adding registrations for a number of classes that MarkDuplicatesSpark needs that weren't registered yet

notably, BAMRecord wasn't registered to use the correct serializer which could cause major inefficiencies
it's not clear what circumstances we're serializing BAMRecord instead of SAMRecordToGATKReadAdapter so how much this will help is not obvious

src/main/java/org/broadinstitute/hellbender/engine/spark/GATKRegistrator.java

@@ -3,7 +3,7 @@
 import com.esotericsoftware.kryo.Kryo;
 import com.esotericsoftware.kryo.serializers.FieldSerializer;
 import de.javakaffee.kryoserializers.UnmodifiableCollectionsSerializer;
-import htsjdk.samtools.SAMRecord;
+import htsjdk.samtools.*;
 import org.apache.spark.serializer.KryoRegistrator;
 import org.bdgenomics.adam.serialization.ADAMKryoRegistrator;
 import org.broadinstitute.hellbender.utils.read.SAMRecordToGATKReadAdapter;
@@ -17,7 +17,7 @@
  */
 public class GATKRegistrator implements KryoRegistrator {
 
-    private ADAMKryoRegistrator ADAMregistrator;
+    private final ADAMKryoRegistrator ADAMregistrator;
 
     public GATKRegistrator() {
         this.ADAMregistrator = new ADAMKryoRegistrator();
@@ -43,6 +43,13 @@ public void registerClasses(Kryo kryo) {
         kryo.register(SAMRecordToGATKReadAdapter.class, new SAMRecordToGATKReadAdapterSerializer());
 
         kryo.register(SAMRecord.class, new SAMRecordSerializer());
+        kryo.register(BAMRecord.class, new SAMRecordSerializer());
+
+        kryo.register(SAMFileHeader.class);
+        kryo.register(SAMFileHeader.GroupOrder.class);
+        kryo.register(SAMFileHeader.SortOrder.class);
+        kryo.register(SAMProgramRecord.class);
+        kryo.register(SAMReadGroupRecord.class);
 
         //register to avoid writing the full name of this class over and over
         kryo.register(PairedEnds.class, new FieldSerializer<>(kryo, PairedEnds.class));