Resolve "Allowing to configure mail sender (From)"

Closes #607 (closed)

Currently, the sending email addresses (From field) are hardcoded in the i18n files. Before, it was possible to modify these addresses but via the configuration file. Now it is not possible anymore.

see:

• mail r2d2@asqatasun.org
• mail no-reply@asqatasun.org

Improvement

Allow to change sender of emails when launching application.

Before	After (default)	After (custom)
hardcoded r2d2@asqatasun.org hardcoded no-reply@asqatasun.org	asqatasun@example.com	custom email
r2d2@asqatasun.org	asqatasun@example.com	asqatasun@your-organisation.com
no-reply@asqatasun.org	asqatasun@example.com	asqatasun@your-organisation.com