Added language selector in settings for Galician, Basque

Added a custom language selector in settings to make Galician and Basque translations visible. The selector control is in the Settings menu, right above the manual link. 

The modifications that allow setting of a custom locale are based on this post:

http://stackoverflow.com/questions/2264874/changing-locale-within-the-app-itself

The control itself is a radio button with 3 options:

- Default terminal setting -> Takes locale from device
- Galician -> Forces loading the locale "gl"
- Basque -> Forces loading the locale "eu"

When the users selects an option, the preferred locale is saved to preferences with the key "pref_locale". Changing this option requires restart of the app to see the changes. If the user does so, the next time the app starts it loads all the app strings in the last selected language.