[2.0] DDC-191 - Added test that verifies mixed case identifier generation is default, when no case mode is set due to previous commit for DDC-169 ticket.

[2.0] DDC-169 - Changed AbstractPlatform and AbstractSchemaManager Constraint API to accept Constraint interface, which is implemented by indexes and foreign keys.

[2.0] DDC-169 - Changed AbstractPlatform and AbstractSchemaManager and children to accept Table, Index and ForeignKey instances for the respective create*() methods.

[2.0] Fixed DDC-103 - Platform::getAlterTableSql() should return an array on all platforms, added doc-blocks on all methods and fixed some.

[2.0] Added functionality to convert a Doctrine 1 schema to Doctrine 2 to help users with upgrading. Lots of other small bug fixes and changes.

[2.0] Made MySqlPlatform default to innodb table engine. Some cleanups while investigating the optimistic locking failures.

[2.0] Test coverage for OFFSET AND LIMIT sql generation for all platforms and Query class with setFirstResult() and setMaxResult()

divided some assertions in various cohesive methods and renamed method names to conform to agile documentation (affects #2316)

[2.0] Started to implement proxy object handling. Introduced a configuration switch for partial objects (allowPartialObjects) that defaults to TRUE. Setting to FALSE enables proxying and lazy-loading.