BibIndex: use human friendly index name

* Adds a more administrator friendly progress display when
  running a BibIndex task in BibSched as it prints the index name
  in addition to the more cryptic index tablename.
  (addresses #1329)

* The same progress display now also tries to give an estimate
  of completed work in percentage.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>