Change several uses of std::list to alternative containers:

*  Performance motivated.
*  Several of these called size() which is O(N) in gcc-4.8.
*  Remove container copy from LedgerConsensusImp::playbackProposals().
*  Addresses RIPD-284.

beast/container/tests/aged_associative_container.test.cpp

@@ -387,10 +387,10 @@ public:
 
     template <class Cont>
     static
-    std::list <typename Cont::value_type>
+    std::vector <typename Cont::value_type>
     make_list (Cont const& c)
     {
-        return std::list <typename Cont::value_type> (
+        return std::vector <typename Cont::value_type> (
             c.begin(), c.end());
     }