Take advantage of new server features

[philbudne]

The web-search server now accepts param cache (on a GET or caching on a POST) to disable caching for testing, or when requests are unlikely to be repeated (a likely case for API use).

More error information is now available from "search" endpoints:

• status: "error"
• note: short message (str(Exception))
• temporary: true or false (would like to have returned 503 for temp errors, but Django thinks it's an internal error) indicating whether ES thinks the error is temporary or permanent. NOTE! I've seen it return permanent with memory "circuit breaker" errors and the query later runs ok.

And may contain the following:

• exception: more detailed message (repr(Exception))
• traceback: a subset of the full exception traceback