added test provided for issue 596

provided by @chuck-jove on
https://github.com/propelorm/Propel/issues/596
order by alias is not supported in mssql. fixes #596 by @chuck-jove
fixed test
Merge pull request #607 from staabm/issue596

added test & fix provided for issue 596
Fixed #617. Proved the issue #617 and fixed it.

Adds now always the `Engine` vendor information in `MysqlSchemaParser` no matter if the build property `addVendorInfo` is true or not, because we need it in `MysqlPlatform` to check whether the table is `InnoDB` and thus with foreignKey support.
If `addVendorInfo` is true, it extracts **all** vendor information (as before).
Added a test that proves the bug and a helper class for more tests like that.
Split the `testForeignKey` into several methods. Added some phpdoc so its cleaer
bump 1.6.9-dev version
Merge branch '1.6'