Added buffer to the console

Added hotkeys to switch between console buffers and to return to the home one
Added clear screen command
Added debug text outputs to the hello command and when loading sh

zombie.sym

@@ -1,48 +0,0 @@
-00000000 zombie.c
-00000000 ulib.c
-00000000 printf.c
-00000340 printint
-00000778 digits.0
-00000000 umalloc.c
-00000a20 freep
-00000a24 base
-00000030 strcpy
-000003f0 printf
-0000032b greeting
-00000250 memmove
-000002fb mknod
-00000150 gets
-000002cb getpid
-00000620 malloc
-000002db sleep
-00000293 pipe
-00000323 getch
-000002f3 write
-000002b3 fstat
-000002a3 kill
-000002bb chdir
-000002ab exec
-0000028b wait
-0000029b read
-00000303 unlink
-0000027b fork
-000002d3 sbrk
-000002e3 uptime
-00000a20 __bss_start
-000000f0 memset
-00000000 main
-00000060 strcmp
-00000333 shutdown
-000002c3 dup
-000001c0 stat
-00000a20 _edata
-00000a2c _end
-0000030b link
-00000283 exit
-00000210 atoi
-000000c0 strlen
-000002eb open
-00000110 strchr
-00000313 mkdir
-0000031b close
-00000590 free