Updating a schema should introduce also schema creation statements in the generated SQL

[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-91 - Fix auto-generation of asset names (foreign keys and indexes) which could lead to exceptions due to auto-quoting of PostgreSQL for example. Now hashing the names with crc32+dechex

DBAL-50 - Explicitly add an index for each foreign key added to a Schema\Table instance. Removed code to FixSchema based on foreign keys, since assumptions now dont apply anymore. Refactored algorithms to check for duplicate or potential overrule indexes into Schema\Index classes, added tests and unified Table API handling these conflicts

[2.0] DDC-312 - Revert annoying View and Trigger variables in Schema instance, complete "View" support by just returning a View instance

[2.0] Refactored Doctrine\DBAL\Schema API a bit Table::createColumn() was inconsistent with all the other methods being add*

[2.0] DDC-169 - Further refactorings, schema max identifier length is now used for asset generation. Added platform-wide test for unique index generation with create table.

[2.0] Fixed PHP Notice in SchemaTest (only variables should be passed by reference...) and a few other cosmetics in various parts.

[2.0] DDC-169 - Savepoint for Refactorings in Schema-Tool - It is now generating DDL according to the old and the new mechanisms in parallel. Equality of generation has been verified on Sqlite, Mysql, Oracle. If Postgres is also verified, the old code will be removed in favour of the new one completly.

[2.0] - DDC-169 - Began refactoring of DBAL code, introduced object notation for a database schema, including Tables, Indexes, Constraints, Sequences and Columns. Added a CreateSql Visitor which transforms a schema object graph into the required SQL statements to create it. Next: Replacing SchemaTool::getCreateSql() with new syntax...