Fixes #931, #1585.

The new config file section looks like this by default:

    haddock
      -- keep-temp-files: False
      -- hoogle: False
      -- html: False
      -- html-location:
      -- executables: False
      -- tests: False
      -- benchmarks: False
      -- all:
      -- internal: False
      -- css:
      -- hyperlink-source: False
      -- hscolour-css:
      -- contents-location: