BB10: More platform integration

- Possibility to send feedback directly from the app.
- "Write a review" menu item: opens TAO Translator in BlackBerry World.

Also, "Share translation" action was renamed into just "Share".
README: What's changed since last release link
BB10: Settings page
Default value support for TranslationInterface::getSettingsValue()
BB10: Support for switching between Dark and Light theme

Closes #33 - Possibility to switch between dark and light theme
N9,SYM: Settings page
N9,SYM: Move items from main menu into Settings page
N9,SYM,SF: Possibility to send feedback directly from the app
SYM: Very slight changes to Main page layout