Unescaping re-added, support limited to schema introspection (#2850 will bring more complete coverage)

@morozov review: According to MySqlPlatform::getListTableColumnsSQL(), the default column is always selected. Removed ??

- Fixed docblocks
- Removed return statements on void methods
- Cleaned up unused private / local variables
- Fixed license issues
- Removed SVN leftovers
- Fixed doctrine-project.org links
- Added line breaks before return statements

Unsigned column properties were never set. In consequence all migrations diff were trying to change the column definition when it was already changed.

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

[DBAL-42] Add support to reverse engineer Comments from MySQL, PostgreSQL and ORacle into Doctrine\DBAL\Schema\Column instances and added comment comparison into Comparator.