Resolved #357 - Allow usage of Parcelable for IHeaders and IFlexible

If you pass the Items or Headers to an Intent as a Parcelable the headers
are recreated as different instances and are shown above each item and not
the whole group. The reason for this of the usage of reference equality
check. We need to use the equal() to fix this issue.

flexible-adapter/src/main/java/eu/davidea/flexibleadapter/FlexibleAdapter.java

@@ -1628,7 +1628,7 @@ private void showAllHeadersWithReset(boolean init) {
 			T item = getItem(position);
 			// Reset hidden status! Necessary after the filter and the update
 			IHeader header = getHeaderOf(item);
-			if (header != sameHeader && header != null && !isExpandable((T) header)) {
+			if (!header.equals(sameHeader) && header != null && !isExpandable((T) header)) {
 				sameHeader = header;
 				header.setHidden(true);
 			}
@@ -4220,7 +4220,7 @@ private void resetFilterFlags(List<T> items) {
 			// Restore headers visibility
 			if (headersShown) {
 				IHeader header = getHeaderOf(item);
-				if (header != sameHeader && header != null && !isExpandable((T) header)) {
+				if (!header.equals(sameHeader) && header != null && !isExpandable((T) header)) {
 					header.setHidden(false);
 					sameHeader = header;
 					items.add(i, (T) header);
@@ -5503,7 +5503,7 @@ private void prepareItemsForUpdate(List<T> newItems) {
 				headersShown = true;
 			}
 			IHeader header = getHeaderOf(item);
-			if (header != sameHeader && header != null && !isExpandable((T) header)) {
+			if (header.equals(sameHeader) && header != null && !isExpandable((T) header)) {
 				header.setHidden(false);
 				sameHeader = header;
 				newItems.add(position, (T) header);