[ticket/12786] Extend profilefield_base_migration.php class

If extensions authors will use profilefield_base_migration.php class as base class for creation of CPFs, the class need to be extended a bit.

At the moment there are two issues with it:

- It does not create entries for PROFILE_FIELDS_LANG_TABLE (as it can't know what fields to create).
- The migration is not "cleaning" the DBMS after purging the extension and leaves everything except the CPF column.


```
	array_merge(array(
		'field_id'	=> $field_id,
		'lang_id'	=> $lang_id,
	), $language_data)
```
instead?