Better error reporting for sphinx

If searchd is not running or cannot be connected to due to misconfiguration, searching for anything produces a "no search results" message indistinguishable from searching for keywords which do not occur anywhere.

I suggest the following:

1. Keep track of any errors retrieved from sphinx.
2. Log errors to error log.
3. If the user is logged in and has admin privileges, show them the actual error instead of "no search results".
4. If user is not an admin tell them there was a problem searching and more information was written to the error log.