D11038: balooctl: Add pruneDb option to remove stale file index entries.

[Michael Heidelbach]

michaelh added a reviewer: michaelh.

REPOSITORY
  R293 Baloo

REVISION DETAIL
  https://phabricator.kde.org/D11038

To: smithjd, #baloo, #frameworks, michaelh
Cc: michaelh, ashaposhnikov, spoorun, nicolasfella, alexeymin