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

Fixed oracle integer/boolean type detection in OracleSchemaManager::_getPortableTableColumnDefinition()

DBAL-62 - There is a diference between maximum length (now 4000, oracle is the smallest possible denominator here) of varchars and the default length (255).