- Fix for
    Bug#28827 Partition test needs archive engine
    Bug#26669 Two tests on partition fail while blackhole engine is missing
  Solution: Move ARCHIVE and BLACKHOLE sub test cases to their own main test.
- The two bugs above + the fact that CSV could be also sometimes not
  available --> Move also CSV sub tests out.
- Minor cleanups
  - Replace error numbers with error names
  - fix typos, wrong comments
  - remove redundant sub test cases
  - add missing drop database
  - SET GLOBAL general_log = default is wrong, = 1 is correct


mysql-test/r/partition.result:
  Updated results
mysql-test/t/partition.test:
  Remove ARCHIVE, BLACKHOLE and CSV related sub test cases.
mysql-test/r/partition_archive.result:
  Expected results
mysql-test/r/partition_blackhole.result:
  Expected results
mysql-test/r/partition_csv.result:
  Expected results
mysql-test/t/partition_archive.test:
  Tests for the partition storage engine in connection with the
  storage engine ARCHIVE.
mysql-test/t/partition_blackhole.test:
  Tests for the partition storage engine in connection with the
  storage engine BLACKHOLE.
mysql-test/t/partition_csv.test:
  Tests for the partition storage engine in connection with the
  storage engine CSV.