Make language configuration more intuitive

[CamiAndrei]

In the version 1.2.4 has been added support for multilingual wikis: #24, but to set the language to each language is not intuitive.
The user needs to click the corresponding language after "Supported languages: en, fr" message.
The message should be replaced with a more explicit message, for e.g.: "Configure the extension for the languages:" .
And the languages should be displayed with the full name, instead of the short names.
Would be also great to change the display to look more like configuration buttons and not messages.