Implement NetworkManager

For now there are two methods:

- `NETWORK:IsUrlAllowed()`: Check whether access to a certain URL is allowed.
- `NETWORK:HttpRequest()`: Perform an HTTP request.

By default access to the network is disabled for all target hosts. It
can be enabled by setting `HttpEnable=1` in the preferences. Individual
hosts have to be added to `HttpAllowHosts` as a comma separated list to
allow access.

See included docs for more details on usage.

extern/IXWebSocket-11.3.2/test/IXHttpTest.cpp

@@ -0,0 +1,53 @@
+/*
+ *  IXHttpTest.cpp
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2019 Machine Zone. All rights reserved.
+ */
+
+#include "catch.hpp"
+#include <iostream>
+#include <ixwebsocket/IXHttp.h>
+#include <string.h>
+
+namespace ix
+{
+    TEST_CASE("http", "[http]")
+    {
+        SECTION("Normal case")
+        {
+            std::string line = "HTTP/1.1 200";
+            auto result = Http::parseStatusLine(line);
+
+            REQUIRE(result.first == "HTTP/1.1");
+            REQUIRE(result.second == 200);
+        }
+
+        SECTION("http/1.0 case")
+        {
+            std::string line = "HTTP/1.0 200";
+            auto result = Http::parseStatusLine(line);
+
+            REQUIRE(result.first == "HTTP/1.0");
+            REQUIRE(result.second == 200);
+        }
+
+        SECTION("empty case")
+        {
+            std::string line = "";
+            auto result = Http::parseStatusLine(line);
+
+            REQUIRE(result.first == "");
+            REQUIRE(result.second == -1);
+        }
+
+        SECTION("empty case")
+        {
+            std::string line = "HTTP/1.1";
+            auto result = Http::parseStatusLine(line);
+
+            REQUIRE(result.first == "HTTP/1.1");
+            REQUIRE(result.second == -1);
+        }
+    }
+
+} // namespace ix