Unused dependency trimming

[Fydar]

Add API for importing assets to force-include them in the build (for assets that serve as the root assets for the game) and allow removal of all assets that are unused.

public IEnumerable<ProjectResourceUpdate> ImportFile(ArchiveFileImporterContext context, IArchiveFile archiveFile)
{
    var update = context.AuthorUpdate(archiveFile.FullName)
        .WithContent(archiveFile);

    // Dependency trimming API
    update.AlwaysInclude(true);

    yield return update;
}

This could be implemented with an IImportProcessor that removes assets at the stage in the build pipeline. This means that a user will be able to customise at which point in the build pipeline the removal of the resources occurs at.

Import = ImportPipeline.Create()
    .UseJsonMetaFiles()
    .UseImporter(new ImageImporter())
    .UseImporter(new JsonImporter())
    .UseProcessor(new ImageProcessor())
    .UseProcessor(new LoggingImportProcessor())
    // Dependency trimming API
    .UseDependencyTrimming()
    .Build();

For optimization purposes, I can also abort the writing of the IContentWriter that was created for the original assets that are no longer going to be included.

[Fydar]

I intend to implement this on my portfolio website as a test-case. It would also be handy if there was a method for producing reports on the imported resources (and the source files that created them) that weren't included in the build.