Fixes an issue when calling `ping()` where `$this->platform` is null. Happened to me because using the `'pdo'` param bypasses the `connect()` method and the platform is never set without explicitly calling the method.

Not sure if this is the most elegant way to deal with this but it worked enough for my purposes so I figured I should submit a PR.

These events don't exist.

The inner connection should be unreferenced, but the property should not be removed from the object

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