rather a lot of changes to make hyperestraier search be a plugin, allowing

rather a lot of changes to make hyperestraier search be a plugin, allowing
for other types of search engine plugins if wanted, and also opening up a
lot of new possibilities for other kinds of plugins later

some notable changes along the way:

- lots of new hook types: cgi, render, delete
- wrapper files fixed to support config strings with newlines in them
- HEADERCONTENT in page template useful for plugins. Probably needs to be
  expanded to more such for other places plugins might want to add content.
- remove unnecessary wrappers field from config info stored in wrappers