added content

• blue color theme
• cactus scenery
• desert map

update

• make it easier to add custom themes and localization files
• add dedicated parameters for each game mode (for now there's only two: last survivor, higher score)
• add dedicated "Game Mode" icon
• allow support for new keyboard layouts to be added easily
• update directional key icons (arrows instead of triangles)
• update installer script to include the new "themes" folder
• Controls menu: align directional keys table's rows to the left
• no command prompt should appear when launching the game's executable

bugfix

• add special characters back in french localization file (using unicode characters)
• bundled shapes don't levitate
• wrong color for disabled buttons