add lightweight block propagation ("fluffy blocks")

Added a new command to the P2P protocol definitions to allow querying for support flags.

Implemented handling of new support flags command in net_node. Changed for_each callback template to include support flags. Updated print_connections command to show peer support flags.

Added p2p constant for signaling fluffy block support.

Added get_pool_transaction function to cryptnote_core.

Added new commands to cryptonote protocol for relaying fluffy blocks.

Implemented handling of fluffy block command in cryptonote protocol.

Enabled fluffy block support in node initial configuration.

Implemented get_testnet function in cryptonote_core.

Made it so that fluffy blocks only run on testnet.

src/cryptonote_core/cryptonote_core.cpp

@@ -915,6 +915,11 @@ namespace cryptonote
     m_mempool.get_transactions(txs);
     return true;
   }
+  //-----------------------------------------------------------------------------------------------  
+  bool core::get_pool_transaction(const crypto::hash &id, transaction& tx) const
+  {
+    return m_mempool.get_transaction(id, tx);
+  }  
   //-----------------------------------------------------------------------------------------------
   bool core::get_pool_transactions_and_spent_keys_info(std::vector<tx_info>& tx_infos, std::vector<spent_key_image_info>& key_image_infos) const
   {