Change Oracle sequence generation to match what is being created by ORM and other platforms in the form of $table_$column_SQL instead of $table_SEQ

Fix for nasty bug that happens when there are 2 or more schemas with tables that have the same name. Since all the AbstractPlatform classes get only the table name using ALL_* schema tables is dangerous because the owner is never supplied.

The other possible solution is to use the ALL_* tables but in each of the methods to fetch the owner before actualy querying them.

DDC-1282 - Remove overprotective casting of days/months to integer, which prevents passing columns as days. The platform is not responsible for escapsing, the DQL parser already does it way before generating the sql statements.

DBAL-112, DBAL-113 - Implement AbstractPlatform::getAlterSequenceSQL() and fix comparator code for sequences

[DBAL-45] Add reserved keywords feature through platforms and as a validator for any Schema instance with subelements. Add Command to check for reserved keywords in current database.

DBAL-88 - Change index retrieval of MySQL to use information_schema.statistics which avoids errors when using reserved words for table names (for example in database driver).

DBAL-84 - Fix VARCHARs being silently set to 255 chars when larger than Maxlength. Now they are converted to Text/CLOB fields automatically. Refactored the VARCHAR code considerably.

[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.

DBAL-62 - There is a diference between maximum length (now 4000, oracle is the smallest possible denominator here) of varchars and the default length (255).