missing call to logger in Connection->exec(), cleanups

Allow empty host to PDOOracle

SQLParserUtils triggered an error when feeding it Type instances instead of PDO param type ints

Log transaction statements

[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.

Removed is_int check and converted both comparisons into equality comparisons when expanding list parameters.

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

[DBAL-216] Add Sqlsrv as driver

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-211] Fix bug with elements in default schema not filtered for really being in the default search path.