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

kill.sym

@@ -1,48 +0,0 @@
-00000000 kill.c
-00000000 ulib.c
-00000000 printf.c
-00000370 printint
-000007bc digits.0
-00000000 umalloc.c
-00000a74 freep
-00000a78 base
-00000060 strcpy
-00000420 printf
-0000035b greeting
-00000280 memmove
-0000032b mknod
-00000180 gets
-000002fb getpid
-00000650 malloc
-0000030b sleep
-000002c3 pipe
-00000353 getch
-00000323 write
-000002e3 fstat
-000002d3 kill
-000002eb chdir
-000002db exec
-000002bb wait
-000002cb read
-00000333 unlink
-000002ab fork
-00000303 sbrk
-00000313 uptime
-00000a74 __bss_start
-00000120 memset
-00000000 main
-00000090 strcmp
-00000363 shutdown
-000002f3 dup
-000001f0 stat
-00000a74 _edata
-00000a80 _end
-0000033b link
-000002b3 exit
-00000240 atoi
-000000f0 strlen
-0000031b open
-00000140 strchr
-00000343 mkdir
-0000034b close
-000005c0 free