Invader Generator, v0.2

Invader Generator, v0.2

Made the code more generic. Default settings are defined in the InvaderSettings class. An instance is created and passed to the Invader and then PixelBox class. 

Custom settings can be defined on settings creation or by passing a value to the settings attribute. 
- pixelH, the number of horizontal pixels
- pixelV, the number of vertical pixels
- pixelSize, the size of each pixel box
- gap, the gap to leave between the invaders when lining them up horizontally or vertically. 
- borderColor, the borderColor for each pixel box.
- backgroundColor, the backgroundColor for each pixel box. 
- pattern, to pass on a pattern that define the location of the pixel boxes. 

Rather than define a backgroundColor you can define a list of colors to pick randomly from
- colors: [0xFF0000, 0xFF00FF]
- colors: [InvaderSettings.BLUE, InvaderSettings.YELLOW]

Any parameter left undefined will be replaced with the default value. 