Add total number of commitments to getblockchaininfo

src/zcash/IncrementalMerkleTree.hpp

@@ -75,6 +75,8 @@ public:
                parents.size() * 32; // parents
     }
 
+    size_t size() const;
+
     void append(Hash obj);
     Hash root() const {
         return root(Depth, std::deque<Hash>());