Use BepInEx and NuGet feed for most packages

I cannot find the exact versions that COM uses for some packages so I
settled for matching at least major and minor.

Directory.Build.props

@@ -6,4 +6,11 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="COM3D2.GameLibs" Version="2.17.0-r.0" />
+    <PackageReference Include="UnityEngine" Version="5.6.1" />
+    <PackageReference Include="BepInEx.BaseLib" Version="5.4.19" />
+    <PackageReference Include="HarmonyX" Version="2.9.0" />
+  </ItemGroup>
+
 </Project>

NuGet.Config

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <add key="BepInEx" value="https://nuget.bepinex.dev/v3/index.json" />
+  </packageSources>
+</configuration>

src/MeidoPhotoStudio.Converter/MeidoPhotoStudio.Converter.csproj

@@ -6,18 +6,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Reference Include="..\..\lib\Assembly-CSharp.dll" />
-    <Reference Include="..\..\lib\UnityEngine.dll" />
-    <Reference Include="..\..\lib\Ionic.Zlib.dll" />
-    <Reference Include="..\..\lib\ExIni.dll" />
-    <Reference Include="..\..\lib\BepInEx.dll" />
-  </ItemGroup>
-
-  <ItemGroup>
     <ProjectReference Include="..\MeidoPhotoStudio.Plugin\MeidoPhotoStudio.Plugin.csproj" />
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="ExIni" Version="1.0.2" />
     <PackageReference Include="LZMA-SDK" Version="18.1.0" />
   </ItemGroup>
 

src/MeidoPhotoStudio.Plugin/MeidoPhotoStudio.Plugin.csproj

@@ -1,14 +1,12 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <ItemGroup>
-    <Reference Include="..\..\lib\Assembly-CSharp.dll" />
-    <Reference Include="..\..\lib\Assembly-CSharp-firstpass.dll" />
     <Reference Include="..\..\lib\Assembly-UnityScript-firstpass.dll" />
-    <Reference Include="..\..\lib\UnityEngine.dll" />
-    <Reference Include="..\..\lib\Newtonsoft.Json.dll" />
-    <Reference Include="..\..\lib\Ionic.Zlib.dll" />
-    <Reference Include="..\..\lib\BepInEx.dll" />
-    <Reference Include="..\..\lib\0Harmony.dll" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Ionic.Zlib" Version="1.9.1.*" />
+    <PackageReference Include="Newtonsoft.Json" Version="10.0.*" />
   </ItemGroup>
 
   <ItemGroup>