Merge for new release 2.3.0

Fixed mismatching method signatures (API)

* PW-455: Support partial refunds for open invoice payment methods

* PW-455: Use Plugin(Interceptor) instead of Event and Observer

* PW-455: Removed observer reference

* PW-455: Refactor

* PW-455: Refactor

* PW-455: Removed plugin and added check on invoice

* PW-256: Added multiple partial captures for OpenInvoice payments

* PW-256: Added adyen_invoice table, added support for acquirerReference.

* PW-256: Moved OpenInvoiceLineData function in the helper. refactored getItemVatAmount, changed description of the entityID

* PW-256: Refactor openinvoicedata functions

* PW-256: Refactor __construct

Use store scope when populating HPP methods

Update README.md

[VM-336] +: Made return path (checkout/cart) configurable

showInStore missing on some groups

Replace "Place order" by "Place Order" like Magento

Compatibility with PHPUnit 6

Create nl_NL.csv

Show payment link in admin for remaining order balance

When not supported by browser, the link can still be copied manually

* Fix for returning only selected boleto types in checkout

* Fix not showing boleto type field if only one field is configured

* Added validation of the Boleto Types field

This link only shows when the original order payment method is an
Adyen method, the total due is greater than 0 and the invoiced total
is greater than 0.

Made payment URL generation method public

Place Order function race condition fix

[VM-233] +: isButtonActive function for databind +: set isPlaceOrderActionAllowed on start place order event

Pw 352

Added boleto logo

Remove Cron controller should not be accessable from browser,

* Fix PayPal capture mode

* Changed variable name to manualCapturePayPal