Adding Level adapter support for Sublevel and Multilevel

[mshick]

I needed support for both these for a current project. Fairly straightforward implementation using Net.connect().

Summary of changes:

• Update local module requires to support LevelUp and Multilevel as well as Level
• Update adapter init to branch logic for Multilevel vs. plain Level
• Update config to support a sublevel name, and handle in init (will attempt a local require for level-sublevel, and throw an error if it doesn't exist).
• Update config to disable / modify keyPrefix (to avoid duplicate prefixes when using sublevels)
• Add connect/disconnect methods which I really uncertain of. Docs indicate they are just for getting connection feedback, but the mongo adapter seems to use them for acquiring the db connection itself. I followed the docs.

[mde]

Adapter adapters, this is great! Excellent work, thanks for implementing this. I'm going to get the tests passing then merge this.

[mshick]

Thanks! Adapter adapters sounds scary to me, but hopefully this is a special case...

[mde]

Exactly -- "adapters all the way down" doesn't sound optimal. The tests were breaking due to a recent Jake update. Should be merged shortly. :)