Replace LocalEventLoopGroup with DefaultEventLoopGroup

Motivation:

LocalEventLoopGroup and LocalEventLoop are not really special for LocalChannels.  It can be used for other channel implementations as long as they don't require special handling.

Modifications:

- Add DefaultEventLoopGroup and DefaultEventLoop
- Deprecate LocalEventLoopGroup and make it extend DefaultEventLoopGroup
- Add DefaultEventLoop and remove LocalEventLoop
- Fix inspector warnings

Result:

- Better class names.