Review the CLI.

The new commands make more sense now. We got rid of the non-implemented
per-table operation modes that aren't interesting anyway, and implement
actually interesting sub-commands now with the schema manipulation bits.

  pgcopydb
    copy-db  Copy an entire database from source to target
  + dump     Dump database objects from a Postgres instance
  + restore  Restore database objects into a Postgres instance
  + list     List database objects from a Postgres instance
    help     print help message
    version  print pgcopydb version

  pgcopydb dump
    schema     Dump source database schema as custom files in target directory
    pre-data   Dump source database pre-data schema as custom files in target directory
    post-data  Dump source database post-data schema as custom files in target directory

  pgcopydb restore
    schema     Restore a database schema from custom files to target database
    pre-data   Restore a database pre-data schema from custom file to target database
    post-data  Restore a database post-data schema from custom file to target database

  pgcopydb list
    tables   List all the source tables to copy data from
    indexes  List all the indexes to create again after copying the data