- 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