D16166: Pass the FileIndexerConfig as const to the individual indexers

[Stefan Brüns]

bruns added a reviewer: dfaure.

REPOSITORY
  R293 Baloo

REVISION DETAIL
  https://phabricator.kde.org/D16166

To: bruns, #baloo, #frameworks, poboiko, ngraham, dfaure
Cc: kde-frameworks-devel, ashaposhnikov, michaelh, astippich, spoorun, ngraham, 
bruns, abrahams