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

ls.sym

@@ -1,51 +0,0 @@
-00000000 ls.c
-00000e04 buf.0
-00000000 ulib.c
-00000000 printf.c
-00000650 printint
-00000ad4 digits.0
-00000000 umalloc.c
-00000e14 freep
-00000e18 base
-00000340 strcpy
-00000060 fmtname
-00000700 printf
-0000063b greeting
-00000560 memmove
-0000060b mknod
-00000460 gets
-000005db getpid
-00000930 malloc
-000005eb sleep
-000005a3 pipe
-00000633 getch
-00000603 write
-000005c3 fstat
-000005b3 kill
-000005cb chdir
-000005bb exec
-0000059b wait
-000005ab read
-00000613 unlink
-0000058b fork
-000005e3 sbrk
-000005f3 uptime
-00000e04 __bss_start
-00000400 memset
-00000000 main
-00000370 strcmp
-00000643 shutdown
-000005d3 dup
-000004d0 stat
-00000e04 _edata
-00000e20 _end
-0000061b link
-00000100 ls
-00000593 exit
-00000520 atoi
-000003d0 strlen
-000005fb open
-00000420 strchr
-00000623 mkdir
-0000062b close
-000008a0 free