Expose the table properties to application

Summary: Provide a public API for users to access the table properties for each SSTable.

Test Plan: Added a unit tests to test the function correctness under differnet conditions.

Reviewers: haobo, dhruba, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16083

include/utilities/stackable_db.h

@@ -148,6 +148,10 @@ class StackableDB : public DB {
     return db_->GetDbIdentity(identity);
   }
 
+  virtual Status GetPropertiesOfAllTables(TablePropertiesCollection* props) {
+    return db_->GetPropertiesOfAllTables(props);
+  }
+
   virtual Status GetUpdatesSince(SequenceNumber seq_number,
                                  unique_ptr<TransactionLogIterator>* iter)
     override {