Added functions for opening files and reading bitmap image files

|SOURCE|
[Bitmap]
* Loads a 256-colour bitmap from disk and stores it in an IMAGE struct
[File]
* File loading and closing functions
[Image]
* The native format for images, with the upper-left co-ordinate being the
  origin, going positive along the right and bottom for X and Y, respectively
* Functions are provided for creating and destroying an image, as well as
  drawing an image to the screen
[Video]
* Added functions for drawing raster lines to the screen
* Added a function to set the palette data
[Main]
* The most recent addition is displaying an image file from disk, currently it
  is not displaying properly

|CONTENT|
[Fonts/Ubuntu Mono 18px]
* Font