Redo a bunch of channel stuff, finally implementing Channel and User into Connection. Also, merge developer_mode and logging config sections, as only logging developer options were left there.
Move core_tracker to tracking plugin, and reduce it's functionality a bunch. All of that stuff is now handled by Connection directly iteself.

Also, add a CaseInsensitiveDictionary class in util/dictionaries.py, so that connections and channels can have case-insensitive dicts for channels and users.