Issue #21 - Warn the user if no external storage is found
Issue #22 - Use sp for text sizes. dp for margins.
* For text sizes, convert dp units to sp, in order to be scaled
based on users configuration.
* Use a bare minimum of 14sp, in order to increase the readability in
some cases.
* Match Settings and Preferences screens text sizes.
* Use dp units instead of dip, just for the sake of consistency.
Merge branch 'develop' into feature/localization
Issue #4 - Use match_parent constant instead of fill_parent
Issue #4 - Remove unused code
Issue #20 - Split app locale from device locale

* Use a custom locale for the application.
* Add application class to hold Locale shared information
* Update string resources
Issue #20 - One locale to rule them all

* Use the application locale to display UI & survey translations.
* Remove multiple languages display.
Issue #4 - Remove useless return