caching: Use separate caches for config variants and other contexts. * The `_cache` directory is now organized in multiple "sub-caches" for different contexts. * A new context is created when config variants or overrides are applied. * `serve` context uses a different context that the other commends, to prevent the `bake` command's output from messing up the preview server (e.g. with how asset URLs are generated differently between the two). * Fix a few places where the cache directory was referenced directly.

{
  "name": "PieCrust",
  "version": "0.0.1",
  "private": "true",
  "dependencies": {
    "bootstrap": "~3.3.2"
  }
}