epee: optionally restrict HTTP service to a configurable user agent

This is intended to catch traffic coming from a web browser,
so we avoid issues with a web page sending a transfer RPC to
the wallet. Requiring a particular user agent can act as a
simple password scheme, while we wait for 0MQ and proper
authentication to be merged.

src/daemon/command_server.cpp

@@ -37,10 +37,11 @@ namespace p = std::placeholders;
 t_command_server::t_command_server(
     uint32_t ip
   , uint16_t port
+  , const std::string &user_agent
   , bool is_rpc
   , cryptonote::core_rpc_server* rpc_server
   )
-  : m_parser(ip, port, is_rpc, rpc_server)
+  : m_parser(ip, port, user_agent, is_rpc, rpc_server)
   , m_command_lookup()
   , m_is_rpc(is_rpc)
 {