Register custom URL protocol handler

Demo of registering custom URL protocol handler.

1. We register my-packed-data:/ protocol to read data from a ZIP file. The demo code shows 2 approaches to register the handler:

   • When USE_ZIP_URL_HANDLER symbol is not defined: Use a generic way to register URL handler using CastleDownload.RegisterUrlProtocol.

   • When USE_ZIP_URL_HANDLER symbol is defined: Use TCastleZip and TCastleZip.RegisterUrlProtocol to register the handler. This is simpler and more efficient, but it serves a more specific use case: it allows to read contents from a ZIP file by accessing my-packed-data:/... URLs.

2. Furthermore, we use ApplicationDataOverride to load game data from this protocol. This way castle-data:/my_image.png will actually get data from my-packed-data:/my_image.png.

   This is done in the same way, regardless of whether USE_ZIP_URL_HANDLER symbol was defined or not, so regardless of how the my-packed-data:/... protocol was registered.

In effect, we read game data from a ZIP file, but you use castle-data:/ as usual.

TODO

Migrate to use UI designed by CGE editor and use TCastleView.