Add multiple caching mechanisms about orchid HOT 1 CLOSED

There should be multiple levels of caching, depending on the need.

• Build Cache
  • In-Memory
  • Purpose: hold onto resources that cannot change during the course of a build, but may change between builds.
  • Examples: A template engine's template cache, Orchid resource cache, Orchid template resolution cache
• Task Cache
  • In-Memory
  • Purpose: Since only one task is run per Orchid lifetime, this basically means the caching of anything that is not expected to change significantly during a normal development session.
  • Examples: Particularly expensive resource sources (such as HTTP calls to a headless CMS), and other things which can afford to not be current during a single development session, but are expected to be current every time Orchid is instantiated. Generic HTTP GET calls would likely be cached at this level.
• Lifetime Cache
  • On-disk, checked into git
  • Purpose: These are items that are cached to a local directory and checked into git, so that they never need to be looked up again. This is useful for things that you know aren't going to change for a very long time, and once it has been downloaded once it really doesn't need to be downloaded again.
  • Examples: External assets referenced from a CDN, but downloaded locally; static assets aren't going to change, because changes necessarily mean a different URL, and thus a different resource. OEmbeds might also be useful to cache here, if your site embeds a lot of content

from orchid.