dictionary changes; new Wordy command with completion list

Cover's issues related in #1 and #5 where prefixes are desired.

Commands like WeakWordy are still available, but deprecated. Use the new `Wordy` command instead, such as 

```
:Wordy weak
```

Or better yet use the recently-added ring feature.

Various changes to existing dictionaries. Starting to document the sources in the headers of each dictionary.