Add optional delayed loading of assets loaded using a constructor

[fatcerberus]

Support has recently been added to Oozaru to allow the use of asset-loading constructors such as new Sound() and new Shader(). This is enabled by loading the resource in the background and swapping it in via a promise reaction once loading is complete. For the most part this works well, but certain things, such as shader.clone(), are difficult--perhaps even impossible--to support before an asset is fully loaded.

Add an option to miniSphere to artificially delay loading until the next frame, so that synchronous calls which would throw in Oozaru due to an unloaded resource also have a chance to throw in miniSphere for the same reason. This may help to catch errors in code intended to be cross-compatible.

[fatcerberus]

I’m thinking this is best implemented as a flag in the development section in the manifest. This section is automatically ignored by the production engine.