add rapidjson as git submodule

Author: kapilratnani

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "NppJSONViewer/external/rapidjson"]
+	path = NppJSONViewer/external/rapidjson
+	url = https://github.com/kapilratnani/rapidjson

NppJSONViewer/NPPJSONViewer.vcxproj

@@ -77,15 +77,17 @@
     <LinkIncremental Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</LinkIncremental>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
-    <IncludePath>$(SolutionDir)..\thirdparty\rapidjson\include;$(IncludePath)</IncludePath>
+    <IncludePath>$(SolutionDir)external\rapidjson\include;$(IncludePath)</IncludePath>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
-    <IncludePath>$(SolutionDir)..\thirdparty\rapidjson\include;$(IncludePath)</IncludePath>
+    <IncludePath>$(SolutionDir)external\rapidjson\include;$(IncludePath)</IncludePath>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
-    <IncludePath>$(SolutionDir)..\thirdparty\rapidjson\include;$(IncludePath)</IncludePath>
+    <IncludePath>$(SolutionDir)external\rapidjson\include;$(IncludePath)</IncludePath>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <IncludePath>$(SolutionDir)external\rapidjson\include;$(IncludePath)</IncludePath>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" />
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
     <ClCompile>
       <Optimization>Disabled</Optimization>