Remove most glossary returns from "!define"

Example of the bad case:
```
vaasatog> Flash: A keyword ability that lets a player play a card any time they could cast an instant. See rule 702.8, "Flash."
702.8a. Flash is a static ability that functions in any zone from which you could play the card it's on. "Flash" means "You may play this card any time you could cast an instant."
```

The majority of cases don't gain much from including the glossary entry in the response. We'd need to work out sorting the good from the bad, but this can help reduce noise in channels.

Start at the !define command handler and trace how glossary entries are selected and returned. Use the Flash example as a baseline, determine which glossary responses are useful enough to keep, and verify that typical !define replies contain less unnecessary glossary text without losing needed rules information.

Written by the indexing model from the issue text.