Simplewallet should now resolve urls to addresses

Simplewallet should now do a DNS query on an address if it fails to
convert the given string to a binary representation of an address
(base58->binary).  It will prompt the user, telling of what the "url"
passed was, what monero address it translated to, and whether or not
DNSSEC validation was a success, and ask for a confirmation that these
are all acceptable.

src/simplewallet/simplewallet.cpp

@@ -30,6 +30,7 @@
 
 #include <thread>
 #include <iostream>
+#include <sstream>
 #include <boost/lexical_cast.hpp>
 #include <boost/program_options.hpp>
 #include <boost/algorithm/string.hpp>
@@ -909,10 +910,60 @@ bool simple_wallet::transfer(const std::vector<std::string> &args_)
   {
     cryptonote::tx_destination_entry de;
     if(!get_account_address_from_str(de.addr, m_wallet->testnet(), local_args[i]))
+    {
+      // if treating as an address fails, try as url
+      bool dnssec_ok = false;
+      std::string addr_from_dns;
+      std::string url = local_args[i];
+
+      // attempt to get address from dns query
+      addr_from_dns = tools::wallet2::address_from_url(url, dnssec_ok);
+
+      // if string not empty, see if it's an address
+      if (addr_from_dns.size())
+      {
+        if (get_account_address_from_str(de.addr, addr_from_dns))
+        {
+          // if it was an address, prompt user for confirmation.
+          // inform user of DNSSEC validation status as well.
+
+          std::string dnssec_str;
+          if (dnssec_ok)
+          {
+            dnssec_str = "DNSSEC validation PASSED!";
+          }
+          else
+          {
+            dnssec_str = "DNSSEC validation FAILED!";
+          }
+          std::stringstream prompt;
+          prompt << "For URL: " << url
+                 << "," << dnssec_str
+                 << " Monero Address = " << addr_from_dns
+                 << std::endl
+                 << "Is this OK? (Y/n) "
+          ;
+
+          // prompt the user for confirmation given the dns query and dnssec status
+          std::string confirm_dns_ok = command_line::input_line(prompt.str());
+          if (confirm_dns_ok != "Y" && confirm_dns_ok != "y" && confirm_dns_ok != "Yes" && confirm_dns_ok != "yes")
+          {
+            fail_msg_writer() << "User terminated transfer request, disagreed with dns result from url: " << url;
+            return true;
+          }
+        }
+        else
+        {
+          fail_msg_writer() << "Failed to get a monero address from: " << local_args[i];
+          return true;
+        }
+      }
+      else
       {
         fail_msg_writer() << "wrong address: " << local_args[i];
         return true;
       }
+    }
 
     bool ok = cryptonote::parse_amount(de.amount, local_args[i + 1]);
     if(!ok || 0 == de.amount)