Translate Pixel Dungeon

Changes were made to translate the game.
* Including error handling when the character is not found in the font files;
* Creating procedures to return the strings, according the language context;
* Created treatment to convert the special characters when it does not exist in the font files.

**NOTE:** This Pull Request will not affect the remainder of the game, and can be applied without changing the [Pixel-Dungeon](https://github.com/watabou/pixel-dungeon) repository.