COD: no need to hide in admin

Also fixes a fatal error when WC()->payment_gateways()->get_available_payment_gateways() is called in the admin
Closes #5424
COD: check if cart is available before checking if it needs shipping
Consistence

Way to remove complete <h2> tag also consistence syntax like templates/single-product/tabs/additional-information.php
hide number input buttons in firefox 29 and later
defined a min value to cart quantity input
Use WP SEO class method rather than deprecated fn

Notice: wpseo_get_value is deprecated since version WPSEO 1.5.0! Use
WPSEO_Meta::get_value() instead.
Merge pull request #5436 from claudiosmweb/fix-qty-input-firefox29

Hide number input buttons in firefox 29 and later
Merge pull request #5437 from claudiosmweb/feature-cart-qty-min-value

Define a min value to cart quantity input
Merge pull request #5435 from dimitrov-adrian/patch-9

Consistence
Merge pull request #5440 from toddlahman/master

Use WP SEO class method rather than deprecated fn
[2.2] Simplified attribute name sanitisation which maintains UTF8 char integrity.

Fixes #5434
[2.2] get_user and get_user_id methods

Closes #5429
Cleaned up logic in email_instructions functions for @splashingpixels
Brahmanbaria & Habiganj missing from the list

We've 64 districts but listed 62, so two states (Districts) were missing from this file 'Brahmanbaria' & 'Habiganj'. 

Reference from Bangladesh Government Website: http://www.bangladesh.gov.bd/index.php?option=com_content&task=view&id=225&Itemid=272

All of 64 districts are listed there!
Brackets
Prevent empty session data being stored until a cookie or session exists to retrieve it.
Merge pull request #5444 from mkrdip/patch-1

Brahmanbaria & Habiganj missing from the list
Merge pull request #5415 from tamarazuk/patch-2

COD: no need to hide in admin
Option to toggle enable_for_virtual for COD, rather than just doing it.

Closes #5399