[2.0][DC-460] Refactored cache bulk deletion methods to use driver specific features to retrieve list of keys. Also, refactored tests
so that all methods are tested for all drivers.

Removed:

- Doctrine\Common\Cache\AbstractCache::count()
- Doctrine\Common\Cache\AbstractCache::deleteAll()

API Changes:

- Doctrine\ORM\AbstractQuery::getResultCacheId() now public

Bugs fixed:

- Doctrine\Common\Cache\AbstractCache::deleteByPrefix() was deleting _every_ key in cache

[2.0][DDC-48][DDC-47] Refactored cache drivers to allow more control over deleting, added namespacing to cache drivers and implemented clear-cache task

[2.0] Streamlined result structures. Hydration improvements: Small overall improvements, large improvement for (joined) fetched collections (~60%). 

[2.0] Moved cache drivers to Common package. Added new annotation parser implementation to Common package. AnnotationDriver in ORM not yet migrated.

[2.0] Refactored cache drivers. Made use of ArrayCache as the metadata cache during a test suite run.

refactorings, a bug fix (#786) and improved performance for the hydration of results from polymorphic queries.

reverting the reorganization done in 3455-3456 in order to make merging my experimental branch to trunk easier.

Preparation for new organization of code in to sub packages. Changed autoload() to work with new structure.

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