The new option 'drop indexes' reuses the existing code to build all the
indexes in parallel but failed to properly account for that fact in the
summary report with timings.
While fixing this, also fix the SQL used to re-establish the indexes and
associated constraints to allow for parallel execution, the ALTER TABLE
statements would block in ACCESS EXCLUSIVE MODE otherwise and make our
efforts vain.
PostgreSQL COPY format is not really CSV but something way easier to
parse. Funnily enough, parsing it as CSV is not that easy, so we add
here a special simple parser for the COPY format.
It should be quite useful too try loading again reject data files from
pgloader after manual fixing, too. It's still missing some documentation
without any good excuse for that, will add soon.
