Added Bottle::conf (as a replacement for Bottle::config)

Features:
  - Full dict() API. It is, in fact, a subclass of dict.
  - Very fast reads (no overhead compared to a native dicts).
  - app.conf.update('dottet.name.space', ...) for the lazy.
  - New app.hook('config') that watches for configuration updates.

Planned Features:
  - Help texts, constraints and other metadata for keys.
  - on_update callbacks for all keys or specific namespaces.
  - app.conf.load_ini(...) and friends.