Backport from HEAD.

#105726 by moshe weitzman. Remove necessity to hard-code theme engine directories since they can change.

- Patch #88287 by asimmonds, dww et al: installer doesn't support modules outside root/modules directory.  Critical bugfix.

- Patch #77919 by chx, eaton, moshe, et al: enable programmaticaly submitted forms via the pull model.

- Clean up some raw output

  Deprecates the primary_links module.

  This patch was much needed.  Thanks Richards!

  NOTE: if some themers could investigate if there is room for improvement
        with regard to theming, that would be awesome.