[src] Makefile differentiates between iso and kernel.

Call 'make iso' or 'make kernel' to create the respective file.
[src] Added VGA and BIOS Video functionality.

WROS is now able to print strings to terminal screen by using the
BIOS video capatilities.

Makefiles have been refactored: the complete path including temporary
files is now created by simply invoking 'make ...'.

Additionally, the Makefile rule 'boot_iso' has been created.

ISSUE: starting the WROS as kernel only (make boot) will not work.
One assumption is that QEMU treats the kernel in a different way than
an ISO image.