Update default dataset view file settings

[luistoptal]

Pull request for issue: #2122

This is a pull request for the following functionalities:

• Update default active columns for file table in dataset page, according to the ticket description
• Update default number of items per page to 50

How to test?

If you go to any dataset page and open the file settings modal, the default option should be 50. However, the way the protected/components/DatasetPageSettings.php is configured, it used different default settings for live and dev, as can be seen in protected/controllers/DatasetController.php:73, so it is probably sufficient to confirm that the default for live is set correctly

const VIEW_DEFAULT_FILE_COLUMNS = ['name', 'description', 'format_id', 'size', 'location'];

How have functionalities been implemented?

• updated VIEW_DEFAULT_FILE_COLUMNS array
• Updated default items per page in public function getFileSettings
• Added acceptance tests to check the expected defaults

Any issues with implementation?

Since dev uses a different default, the acceptance test added to check the expected defaults will not pass and so I tagged it as broken and added an explanation

Any changes to automated tests?

See above