Revert "initial drchip support (names may still changce)"

This reverts commit 1e898167c739eb351dd4c746d42fae5b19018887.
Add drchip support

Advantages over previous solution:

1. No non-reusable code in autoload/vimpi.vim (code for drchip is highly user 
   dependent).
2. No new file format in db/.
3. No breakage in naming scheme: if author is needed to be specified to avoid 
   naming conflicts, it is specified via `@author` suffix, not `author_` prefix.
4. Sources are updated by the cron job. Original solution did not even contain 
   a URL!
5. No API breakage. I only renamed arguments.