Prevent Connection from maintaining a second reference to an injected PDO object. Previously, if a developer explicitly closed the Connection, only the _conn reference was destroyed, but the _params['pdo'] reference remained and kept the PDO connection alive. By unsetting the _params reference, we maintain only the _conn reference, exactly as if the PDO connection is generated internally.

Intended side effect is not to call extractTypeValues when $types array is empty which it is by default.

 * license
 * author tags
 * doc blocks
 * new lines

 * h/t @stof and @deeky666
 * add two test cases for the general connection test
 * remove the ConnectionException method I added originally

This PR introduces a new PingableConnection interface and exposes
a ping method on \Doctrine\DBAL\Connection. For drivers where no
ping is supported, a \Doctrine\DBAL\ConnectionException is thrown.

Portability wrapper did not properly use the _defaultFetchMode when the method setFetchMode() was used on the Connection

- 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

    Connection#insert(),  Connection#update() and Connection#delete(). Closes GH-271