DHGR Support

Modified the code to use Double Hi-Res Graphics instead of High-Res.
For 560 bits/row two fill bytes are used in the BMP and have to be
jumped.
Support for HGR or DHGR Images

Added a simple check of the horizontal resolution to decide if the HGR
or DHGR mode should be used.
Support for Chat Mauve Mode

Added monochrome and color DHGR initialization depending on the
horizontal resolution. 560x192x1 images are displayed in JACE without
color fringes. Should be tested with real hardware.