Fix bug in DropSchemaSQLCollector dropping tables before sequences which can cause constraint errors

DBAL-54 - Fix sequence drop executed before tables, however sequences mostly depend on tables. Also clean up several test-failures on MSSQL tests and  Oracle Index detection.

[2.0][DDC-92] Fixed. Patch provided by Christian Heinrich. [DDC-274] Started some method renaming. [DDC-142] Fixed (join column names and discriminator column names dont support quoting) [DDC-258] Fixed.

[2.0] DDC-214, DDC-303, DDC-304 - Fix several errors with Schema Inference from Database and Metadata and Comparisons, aswell as related bugs in DatabaseDriver. DDC-305 - Abstracted TRUNCATE command for all platforms.

[2.0] DDC-169 - Introduced handling of schema / database case-sensitivity differences and to allow compability between different platforms.

[2.0] - DDC-169 - Added DropSchemaSql Visitor - Refactored Visitor package a bit, however its still not very appealing to have that much use statements cluttered in the code