Allow port numbers be be specified with a colon: (#4328)

Port numbers can now be specified using either a colon or a space.

Examples:

1.2.3.4:51235

1.2.3.4 51235

- In the configuration file, an annoying "gotcha" for node operators is
  accidentally specifying IP:PORT combinations using a colon. The code
  previously expected a space, not a colon. It also does not provide
  good feedback when this operator error is made.
- This change simply allows this mistake (using a colon) to be fixed
  automatically, preserving the intention of the operator.
- Add unit tests, which test the functionality when specifying IP:PORT
  in the configuration file.
- The RPCCall test regime is not specific enough to test this
  functionality, it has been tested by hand.
- Ensure IPv6 addresses are not confused for ip:port

---------

Co-authored-by: Elliot Lee <github.public@intelliot.com>

src/ripple/core/impl/Config.cpp

@@ -37,6 +37,7 @@
 #include <cstdlib>
 #include <iostream>
 #include <iterator>
+#include <regex>
 #include <thread>
 
 #if BOOST_OS_WINDOWS
@@ -468,6 +469,28 @@ Config::loadFromString(std::string const& fileContents)
     if (auto s = getIniFileSection(secConfig, SECTION_SNTP))
         SNTP_SERVERS = *s;
 
+    // if the user has specified ip:port then replace : with a space.
+    {
+        auto replaceColons = [](std::vector<std::string>& strVec) {
+            const static std::regex e(":([0-9]+)$");
+            for (auto& line : strVec)
+            {
+                // skip anything that might be an ipv6 address
+                if (std::count(line.begin(), line.end(), ':') != 1)
+                    continue;
+
+                std::string result = std::regex_replace(line, e, " $1");
+                // sanity check the result of the replace, should be same length
+                // as input
+                if (result.size() == line.size())
+                    line = result;
+            }
+        };
+
+        replaceColons(IPS_FIXED);
+        replaceColons(IPS);
+    }
+
     {
         std::string dbPath;
         if (getSingleSection(secConfig, "database_path", dbPath, j_))