Feature todolist

[ethanwu10]

Aggregate issue for a bunch of planned features:

Internal:

• parallel container build support (sharding)
• build / layer caching support
• multiple configurations / configuration inheritance (in rcds.yaml for e.g. a staging environment)
  UX:
• advanced asset providers (e.g. tarball, docker container extractor)
  • support nesting (e.g. tarball can have a file originating from inside a docker container
• challenge validation / preview / local build
• build-time templating
• automatic resource allocation (e.g. ports) - lockfile based