adding ability to zip export of multiple tables

[Haran]

Pull Request for Issue #298

Summary of Changes

• php ./cli/joomla.php database:export --folder ./tmp --zip is now able to export all tables and compress them in a single zip file

Testing Instructions

• [ ] Have running Joomla installation
• [ ] Run php ./cli/joomla.php database:export --folder ./tmp --zip
• [ ] Assert in ./tmp folder there's a zip file that contains all tables in corresponding xml files

Documentation Changes Required

No documentation changes required, the current on available on https://docs.joomla.org/J4.x:CLI_Database_Exporter_Importer already states, that php cli/joomla.php database:export --zip should "export the database as .zip file.