Fix for Undefined index: _regular_price, _sale_price, _tax_status, _tax_class, _visibility, _purchase_note

Undefined index appears for: _regular_price, _sale_price, _tax_status,
_tax_class, _visibility, _purchase_note, when fields are empty, for
example.

Notice: Undefined index: _tax_class in
woocommerce\admin\post-types\writepanels\writepanel-product_data.php on
line 678
Hint on documentation of function get_product()

The hint actual says that return void, changed to WC_Product_Simple because $woocommerce->product_factory->get_product() returns WC_Product_Simple, this change is useful for IDEs autocomplete hints
Duplicated German language files for Swiss German locale
Replaced ß with ss for Swiss locale
Replaced Bundesland with Kanton for Swiss locale
Converted .po files to .mo files with msgfmt utility
Update proposal hint on documentation of function get_product()
Update proposal hint on documentation of function get_product()

Update proposal hint on documentation of function `WC_Product_Factory::get_product()` from `void` to an generic `WC_Product`
Update woocommerce-admin-status.php

Added theme info to System Status
adding product meta data to post class
Updated Spanish translation
Finished up the Danish translation (beware of the occasional error!)
Fixed: A few minor typos and unfortunate translations.
Dutch MoPo refresh
Initialize to store address format (#3477)

If the user has not entered an address yet, then the address fields will be displayed in a default order, because the $country will be empty. To fix this and initialize address formats to the stores locale, the $country variable is set to the base_country if it has no value
Japanese Localization

I made Japanese localization files.
Fixed: 'Hej med dig' blev til 'Hej' pga. klager fra en bruger.
Merge pull request #3479 from shoheitanaka/master

Japanese Localization
Merge pull request #3478 from henrikgregersen/master

(#3477) Initialize address formats to the stores locale, instead of use a default.
Merge pull request #3473 from Ramoonus/master

NL refresh