Separate kernel code from test code

Eventually I want the kernel to be loaded from the SD card as well, but
it still needs to separate from user programs.

At some point there should be a folder just for the BIOS, which should
read from the boot block of the SD card and start executing, and thats
it.

sw/kernel/main.c

@@ -0,0 +1,42 @@
+#include <stdint.h>
+#include <conio.h>
+#include <string.h>
+
+#include "devices/board_io.h"
+#include "devices/uart.h"
+#include "devices/mapper.h"
+#include "devices/sd_card.h"
+#include "filesystem/fat.h"
+#include "exec.h"
+
+uint8_t buf[512];
+
+int main() {
+	int i;
+	uint16_t rca;
+
+	clrscr();
+	cprintf("Hello, world!\n");
+
+	for (i = 0; i < 16; i++){
+		//cprintf("Mapping %1xxxx to %2xxxx\n", i, i);
+		mapper_write(i, i);
+	}
+
+	cprintf("Enabling Mapper\n");
+	mapper_enable(1);
+
+	sd_init();
+
+	rca = sd_get_rca();
+	cprintf("rca: %x\n", rca);
+
+	sd_select_card(rca);
+
+	fat_init();
+	exec("/test.o65");
+
+	cprintf("Done!\n");
+
+	return 0;
+}