Add description for OnSchemaAlterTableAddColumn, OnSchemaAlterTableRemoveColumn, OnSchemaAlterTableChangeColumn, OnSchemaAlterTableRenameColumn events

Added parameter "default_dbname" to pdo_pgsql driver which can be used to override the default database

PostgreSQL allows the user to set the application_name is connecting
to database. It is useful for monitoring purposes.
Currently one could just manually add 'application_name=foo' to DSN,
but having a parameter eases setting it using DoctrineBundle.

The first paragraph of section 6.1 has some minor formatting errors (see http://docs.doctrine-project.org/projects/doctrine-dbal/en/latest/reference/transactions.html#transaction-nesting)
Removing a couple of spaces fixes the problem.

Features and changes:
* jsonb can be used with: options={"jsonb"=true}
* OVER is no longer reserved
* LATERAL is now reserved

Fixed inconsistent use of getSQLDeclaration method

The current version is not displayed correctly at
http://docs.doctrine-project.org/projects/doctrine-dbal/en/latest/reference/portability.html

* Remove aliases from examples where they make no sense
* Fixed copy paste error