Added import/not important group headers

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -977,7 +977,13 @@ public class FragmentMessages extends FragmentBase
                 if (!ch && !dh)
                     return null;
 
-                if (pos > 0) {
+                if (EntityMessage.PRIORITIY_HIGH.equals(message.importance)) {
+                    if (pos > 0)
+                        return null;
+                } else if (EntityMessage.PRIORITIY_LOW.equals(message.importance)) {
+                    if (EntityMessage.PRIORITIY_LOW.equals(prev.importance))
+                        return null;
+                } else if (pos > 0) {
                     Calendar cal0 = Calendar.getInstance();
                     Calendar cal1 = Calendar.getInstance();
                     cal0.setMinimalDaysInFirstWeek(4); // ISO 8601
@@ -1024,6 +1030,11 @@ public class FragmentMessages extends FragmentBase
                         vSeparator.setVisibility(View.GONE);
                     }
 
+                    if (EntityMessage.PRIORITIY_HIGH.equals(message.importance))
+                        tvDate.setText(R.string.title_is_important);
+                    else if (EntityMessage.PRIORITIY_LOW.equals(message.importance))
+                        tvDate.setText(R.string.title_is_not_important);
+                    else
                         tvDate.setText(date_week
                                 ? getWeek(message.received, parent.getContext())
                                 : getRelativeDate(message.received, parent.getContext()));

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

@@ -1419,6 +1419,8 @@
     <string name="title_importance_low">Low</string>
     <string name="title_importance_normal">Normal</string>
     <string name="title_importance_high">High</string>
+    <string name="title_is_important">Important</string>
+    <string name="title_is_not_important">Not important</string>
     <string name="title_search_in_text">Search in text &#8230;</string>
     <string name="title_forward">Forward</string>
     <string name="title_resend">Resend</string>