Create index table, add option to remove existing tables.

- For partitioned tables we now create index on czar side and populate
  it from all loaded chunks. By default database name for index is
  qservMeta, can be changed with -i option, use empty string to disable
  index generation.
- New option -e which enable removal of existing tables from database,
  this works both for data (including all chunk tables) and metadata
  (index).