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

DDC-451 - GUID support through a specific GUID Type, SQL Server specific implementation all others fallback to Varchar fields, no automatic default value = new guid support yet.

[DBAL-220] Add support for Index flags and implement support for SQL Server CLUSTERED/NONCLUSTERED and MySQL FULLTEXT.

This is necessary because pdo_sqlsrv still has some little bugs that
prevent it from being used in all use-cases. Additionally only sqlsrv
can make use of the Azure federations features.

[DBAL-204] Sane refactoring of the previous idea. Removed a bunch of code again and implemented proper schema namespacing. Also got the wording right (hopefully) and fixed the algorithms.

[DBAL-195] Fix AbstractSchemaManagertests/Doctrine/Tests/DBAL/Functional/Schema/SchemaManagerFunctionalTestCase.phpdropAndCreateSequence

[DBAL-195] Fix AbstractSchemaManagertests/Doctrine/Tests/DBAL/Functional/Schema/SchemaManagerFunctionalTestCase.phpdropAndCreateSequence