Default isolation level on mysql is REPEATABLE READ

https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_tx_isolation

Fix more occurances of the extending Test bug, "reactivating" a total of 200 tests. SQLAnywhere is missing and is a bit more annyoing to fix, because of a deep inheritance hierachy.

This is at least needed when adding a autoincrement column

[DBAL-166] Default MySQL to UTF8/utf8_general_ci. Allow to set default table options from SchemaConfig.

[DBAL-237] Fix bug when removing and adding an index on the same columns that may be part of a foreign key.

DBAL-126 - Fix bug during table diffs when creating new primary keys, unique constraints were created instead.

DBAL-91 - Fix auto-generation of asset names (foreign keys and indexes) which could lead to exceptions due to auto-quoting of PostgreSQL for example. Now hashing the names with crc32+dechex