New translations and some fixes

Added flags to the translated fields so that the user can easily identify wish fields are locale dependent. (Only added for 'en' and 'pt-PT' locale)
Fixed the product duplicate method so that it supports locales like 'pt-PT', 'en-US', etc...
Added translations to the following fields:
* Spree::Image
	* alt
* Spree::Property
	* presentation
* Spree::ShippingMethod
	* description
* Spree::TaxCategory
	* name
Rake task to copy data from untranslated fields to their specific translations tables.
This changes were based on the 1.2 branch and that's why the pull request is made specifically to that branch.