Vertically center all content in tables

Add spree green and blue colors to variables

Refactor stylesheets a bit. More color fixes.

Fixes #5728
add missing translation editing_country

Closes #5736
fix n+1 for variants index action
Closes #5722
include product for variant stock items update

Closes #5720
refactor taxons controller in backend to follow DRY and break update action into number of smaller methods

Closes #5727
fix n+1 for admin product images

Closes #5723