* [PW-1942]: Admin notifications overview for adyen_notification table

* [PW-1942]: Added notifications overview link to cron information message

* [PW-1942]: Added notifications overview link to cron information message

* [PW-1942]: Adjusted columns, filters and formatting on notifications overview
Moved PSP search URL function to helper since it is now being used in multiple places

* [PW-1942]: Changed virtualType classname to avoid conflicts with Notifications Collection

* [PW-1942]: Implemented getPspReferenceSearchUrl() from library

* [PW-1942]: Unit testing

* [PW-1942]: Applying recommended changes:
* Renamed XML files to adyen_notifications_overview
* Applied PSR2 code styling to CronMessage.php
* Updated Copyright year
* Early return and replaced switch with if and default value in NotificationColumn.php. Also, docs state that success can only be true/false so got rid of third CSS class
* Moved getPspReferenceSearchUrl() method from PHP Lib to Data helper, and added if/else to receive liveEnvironment from notification record instead of receiving test/live string

* [PW-1942]: Code styling

* [PW-1942]: Applying recommended changes:
* Inverted live/test if check
* Removed unnecessary constructor
Co-authored-by: cyattilakiss <42297201+cyattilakiss@users.noreply.github.com>

* PW-1190 add magento info into request

* PW-1190 add unit tests and fix current ones. Add codesniffer and magento/magento-coding-standard to easy validate code within the repo. Add paypal reference as we have a depencency to paypal module as we need it for billing agreements.

* [WIP] Feature/pw 1190 travis (#606)

* add travis file

* add credentials encrypted will only work for local branches

* fix commands

* add ruleset

* update travis to execute all plugin code

* remove params as it is declared into the ruleset. and update version codesniffer

* only fail and show errors not warnings

* added arguments p and n for better visibility and ignoring warning in ruleset xml

* use relative path to fix local check

* Fix Adyen\DataTest

This one is a bit more complex. DataTest depends on some external classes from Magento, so I set up a config and a bootstrap files for testing. While I was at this, I also made the dependencies a bit more strict.

* Update php requirement to match with Magento 2.2.8

    Adyen\Payment\Tests\Helper\DataTest::testFormatAmount
ArgumentCountError: Too few arguments to function Adyen\Payment\Helper\Data::__construct(), 9 passed