Fix a confusion between 'cleanup' and 'skip_cleanup_if_failed' configuration params

#### Problem
Currently we have configuration params `cleanup` and `skip_cleanup_if_failed`.
Despite their names sound similar, they are responsible for completely different things: `cleanup` controls the database re-creation before each test, and `skip_cleanup_if_failed` controls whether records, added by `haveInDatabase()` should be erased after the test.
#### Suggested fix
It would be good to distinguish these two 'cleanups' in documentation and in the names of config params in next major versions.
For example, to rename `cleanup` to `repopulate` (since we have `populate` responsible for initial database creation).