Added support for boot screens

This release adds support for boot screens. By default there is a nice ASCII boot screen that is embedded in the application, however there is support for external custom boot screens by passing a properly converted BGR image to the option splash_image. You can convert the common image formats to BGR by accessing the following website: https://xem.github.io/3DShomebrew/tools/image-to-bin.html. Remember that 3DS top screen has a resolution of 400x240, so you should convert any image to this resolution first.

An example of boot screen image can be seen below:

This release drops support for both debug and cfw_fix options. With splash screen support, the bottom screen is used to show entry information, exactly like the debug option did, so it was removed. cfw_fix was doing something similar to rendering something in the 3DS screens already, so now I am actually rendering something useful in the screen, this option made no sense anymore. However, the benefits of cfw_fix are still there.