Add comment about increment settings version.

src/com/fsck/k9/preferences/AccountSettings.java

@@ -25,6 +25,11 @@ public class AccountSettings {
         Map<String, TreeMap<Integer, SettingsDescription>> s =
             new LinkedHashMap<String, TreeMap<Integer, SettingsDescription>>();
 
+        /**
+         * When adding new settings here, be sure to increment {@link Settings.VERSION}
+         * and use that for whatever you add here.
+         */
+
         s.put("archiveFolderName", Settings.versions(
                 new V(1, new StringSetting("Archive"))
             ));

src/com/fsck/k9/preferences/FolderSettings.java

@@ -20,6 +20,11 @@ public class FolderSettings {
         Map<String, TreeMap<Integer, SettingsDescription>> s =
             new LinkedHashMap<String, TreeMap<Integer, SettingsDescription>>();
 
+        /**
+         * When adding new settings here, be sure to increment {@link Settings.VERSION}
+         * and use that for whatever you add here.
+         */
+
         s.put("displayMode", Settings.versions(
                 new V(1, new EnumSetting(FolderClass.class, FolderClass.NO_CLASS))
             ));

src/com/fsck/k9/preferences/GlobalSettings.java

@@ -26,6 +26,11 @@ public class GlobalSettings {
         Map<String, TreeMap<Integer, SettingsDescription>> s =
             new LinkedHashMap<String, TreeMap<Integer, SettingsDescription>>();
 
+        /**
+         * When adding new settings here, be sure to increment {@link Settings.VERSION}
+         * and use that for whatever you add here.
+         */
+
         s.put("animations", Settings.versions(
                 new V(1, new BooleanSetting(false))
             ));

src/com/fsck/k9/preferences/IdentitySettings.java

@@ -22,6 +22,11 @@ public class IdentitySettings {
         Map<String, TreeMap<Integer, SettingsDescription>> s =
             new LinkedHashMap<String, TreeMap<Integer, SettingsDescription>>();
 
+        /**
+         * When adding new settings here, be sure to increment {@link Settings.VERSION}
+         * and use that for whatever you add here.
+         */
+
         s.put("signature", Settings.versions(
                 new V(1, new SignatureSetting())
             ));