Add hooks for overriding default email inline styles

Currently any h1, h2, h3, a and img tags in a HTML email without a
style attribute will have a default inline style applied to them.
These styles are hard-coded and cannot currently overridden without
patching the source code.

This commit adds two filter hooks that allows the theme developer to
override both the list of tags that have a default style applied to
them and the default styles applied to each tag. The hooks are:

1. woocommerce_email_style_inline_tags
This filter hook returns an array of tags which will have a default
style applied to them - you can both remove and add any tags which
you need for your theme's custom emails.

2. woocommerce_email_style_inline_{name}_tag
This filter is called for every tag name returned by the filter hook
woocommerce_email_style_inline_tags. The styles are passed as an
associative array so you can both add and remove any of the default
styles applied by WooCommerce.

Fixes #3597.
Adding support for percentage factor of additional costs.
removing html decoding from email from name
allowing quotes in store name
Add disabled style to buttons
Compress compiled woocommerce.css
Added woocommerce_get_featured_product_ids() to retrieve featured products IDs within an array
Reloads checkout after registration which fixes #3612, removes some notices preventing login cookie being set, moves cart check for #3162

No perfect solution for #3162. DB locking would probably cause more
issues that its worth, we cannot reliably use transactions as some
clients still use MyIsam. Best to accept orders and deal with stock
conflicts after the fact.
adding esc_html back in to properly escape html from email from name
Ensure product image has title
Merge branch 'master' of https://github.com/woothemes/woocommerce
Merge branch 'master' of https://github.com/woothemes/woocommerce
Fixes from .14
Merge pull request #3723 from ragulka/disabled-buttons

Add disabled style to buttons
Merge pull request #3724 from corsonr/master

Added woocommerce_get_featured_product_ids() to get featured products IDs
Merge pull request #3697 from BFTrick/fix-email-html-encoding

Removing HTML Decoding From Email From Name
woocommerce_address_to_edit #3690
get_categories returns string Closes #3720
Alt changes from .14
Remove echo