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
Fixed my merge gone bad
Readme for cross sells merge fix
Fixed posting shipping method when only one is available

As committed on master branch:
- https://github.com/woothemes/woocommerce/commit/d8ba734d4f71a050df82947d2a8184f7dd8e515d
Fixed query breaking when using some product widgets and closes #3333
Add actions for attribute create/update/delete

As committed on master branch via:
- https://github.com/woothemes/woocommerce/pull/3298
2.0.12 version bump
add a class to the variable pricing table row
use switch case for variation bulk edit. add action hook for new cases
WooCommerce fails to Activate
declared $helpers as a blank array
(to keep things tidy) removed $this->helpers from init().
add admin translation
edit german formal language
Extra escaping on layered nav href to prevent injection
Merge remote-tracking branch 'origin/release-2-0-12'

Conflicts:
	assets/js/frontend/checkout.min.js
	classes/widgets/class-wc-widget-best-sellers.php
	classes/widgets/class-wc-widget-onsale.php
	classes/widgets/class-wc-widget-random-products.php
	classes/widgets/class-wc-widget-recent-products.php
	classes/widgets/class-wc-widget-recently-viewed.php
	readme.txt
	woocommerce.php
Change changelog URL for extension version info to new cloudfront url
Merge pull request #3390 from swicks/master

Fails to activate
Merge pull request #3395 from CoachBirgit/master

edit german formal and add admin language files
Merge pull request #3406 from kloon/master

Extension changelog version info checking
Merge pull request #3385 from helgatheviking/feature/variable-bulk-edit-js

use switch case for variation bulk edit. add action hook for new cases (for #3383)
Merge pull request #3372 from helgatheviking/feature/variable-pricing-meta-tr-class

add a class to the variable pricing table row