[bucket] minor cleanup
[bucket] Make it possible to ask bucket questions

"bucket: how are you?" will no longer teach bucket ('how', 'are', 'you'),
so you can now teach it to reply properly to such questions
[bucket] add "friends" concept

When you preform positive interactions with bucket, it will increase your
"friendly level", and it will decrease with negative interactions.

Bucket will also greet people on join now, but only if it had seen them before,
and it will be more likely to greet people who have a high "friendly level".

This is still WIP, so feedback welcome