add not-again explanation for new archive feature

xwords4/android/app/src/main/java/org/eehouse/android/xw4/BoardDelegate.java

@@ -214,7 +214,11 @@ public class BoardDelegate extends DelegateBase
                     lstnr = new OnClickListener() {
                             public void onClick( DialogInterface dlg,
                                                  int whichButton ) {
-                                archiveAndClose( archiveName, archiveGroup );
+                                makeNotAgainBuilder( R.string.not_again_archive,
+                                                     R.string.key_na_archive,
+                                                     Action.ARCHIVE_ACTION )
+                                    .setParams( archiveName, archiveGroup )
+                                    .show();
                             }
                         };
                     ab.setNeutralButton( R.string.button_archive, lstnr );
@@ -1107,6 +1111,12 @@ public class BoardDelegate extends DelegateBase
             makeOkOnlyBuilder( R.string.after_restart ).show();
             break;
 
+        case ARCHIVE_ACTION:
+            String archiveName = (String)params[0];
+            long archiveGroup = (Long)params[1];
+            archiveAndClose( archiveName, archiveGroup );
+            break;
+
         case ENABLE_SMS_DO:
             post( new Runnable() {
                     public void run() {

xwords4/android/app/src/main/java/org/eehouse/android/xw4/DlgDelegate.java

@@ -84,6 +84,7 @@ public class DlgDelegate {
         TRAY_PICKED,
         INVITE_INFO,
         DISABLE_DUALPANE,
+        ARCHIVE_ACTION,
 
         // Dict Browser
         FINISH_ACTION,

xwords4/android/app/src/main/res/values/common_rsrc.xml

@@ -111,6 +111,7 @@
   <string name="key_notagain_trading">key_notagain_trading</string>
   <string name="key_notagain_hidenewgamebuttons">key_notagain_hidenewgamebuttons</string>
   <string name="key_na_lookup">key_na_lookup</string>
+  <string name="key_na_archive">key_na_archive</string>
   <string name="key_na_browse">key_na_browse</string>
   <string name="key_na_browseall">key_na_browseall</string>
   <string name="key_na_values">key_na_values</string>

xwords4/android/app/src/main/res/values/strings.xml

@@ -1743,6 +1743,14 @@
     <string name="not_again_lookup">This button lets you look up,
       online, the words just played.</string>
 
+    <string name="not_again_archive">Archiving uses a special group
+    called \"Archive\" to store finished games you want to keep. And,
+    since deleting an entire archive is easy, archiving is also a
+    great way to mark games for deletion – if that\'s what you prefer
+    to do.\n\n(Deleting the Archive group is safe because it will be
+    created anew when needed.)
+    </string>
+
       <!--  -->
     <string name="button_move">Move</string>
     <string name="button_newgroup">New group</string>