Releases for UC Correios Quotes

Adds support for estimating shipping cost on product page.

#810934: Value returned from service is actually "declared value" + "shipping"

- fixes optional 'declared value', now it can be send or not to webservice.

- maintenance update, little UI improvements, translation updates for the first stable oficial release.

#656746: Roadmap

#682012: Connection to correios webservice using always the cURL lib

Other improvements:
- updates translations
- updates the README.txt file
- updates the CHANGELOG.txt file

First supported working version.
We're working on the following features before we reach the RC stage:

* Improve error handler to prevent checkout with wrong shipping quotes;
* Add new sources/webservices for obtain the rate quote, for example other webservice instead of official Correios webservice;
* Calculate shipping quotes based on the original location of the product (?).