Define gen_storage

[xandkar]

Look and feel:

• All operations are actually requests to an external resource and therefore can fail, so must live in result monad
• Intuitively, the interface should resemble something like hope_gen_dictionary wrapped in hope_gen_monad
• Lexicon should suggest higher-than-normal latency, such as:
  • store (instead of put)
  • fetch (instead of get)

Semantics? :thought_balloon:

• All completed operations/requests are to be considered ok
• error condition is reserved for uncompleted operations/requests
• Therefore, a completed fetch, that did not find a bound value, is still considered "ok" and should return {ok, none}, whereas completed fetch that did find a bound value returns {ok, {some, Value}}