fixed bootstrapping and asset handling

standalone-openfl-app/CORE_PRINCIPLES_IMPORTANT!.md

@@ -2,4 +2,22 @@
  - Make the code work with the .hxml based workflow
  - don't use compiletime `#if lime` or `#if openfl` as this relies on the openfl and lime build system. We don't use their buildsystems but try to do the same thing they do for the hxcpp based targets. (Native Windows/ Linux compilation)
  - Adhere to the spec outlined in OpenFL_Build_Chain_Asset_System_Deep_dive.md and IMPORTANT_INSTRUCTIONS.md
- 
+ - There is sample code in the Export/haxe directory. We want our own src/ManifestResources.hx to mirror the implementation in Export/haxe/ManifestResources.hx
+ - Mirror preload logic from the Export/haxe directory into our own files.
+ - We also want to preload our assets using a similar approach using the ManifestResource and doing related initialization in ApplicationMain.hx
+
+# Implementation details:
+
+ - macros/AssetMacro.hx
+    - Implement a @:assets decorator that allows specifying assets with the same parameters that openfl/lime use in project.xml
+    - These assets will be defined in Assets.hx
+    - Generate an asset manifest `default.json` in a folder `manifest` in the hxcpp output directory (the same path the built binary gets put into) (get the path for this from the haxe compiler at build time) as defined with the `-cpp` flag in build.hxml
+    - Copy assets into the hxcpp output directory similarly to how lime and openfl do this
+ - Assets.hx
+    - as stated previously, the @:asset decorator will be used here to specify assets for the compiler to copy to the build output directory at compile time
+ - Main.hx
+    - This is the entrypoint for game specific code, no need to touch this yet.
+ - ApplicationMain.hx
+    - This is the actual entrypoint of the application. This sets up the lime/openfl application, window and stage. Also this is responsible for preloading assets.
+ - ManifestResources.hx
+    - This will be left the same as the sample in Export/haxe/ManifestResources.hx