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

sh.sym

@@ -1,69 +0,0 @@
-00000000 sh.c
-00001a20 buf.0
-00000000 ulib.c
-00000000 printf.c
-00000f10 printint
-00001430 digits.0
-00000000 umalloc.c
-00001a84 freep
-00001a88 base
-00000c00 strcpy
-00000fc0 printf
-00000efb greeting
-00000e20 memmove
-00000ecb mknod
-00000370 execcmd
-00000d20 gets
-00000e9b getpid
-000008e0 parsepipe
-00000b90 parsecmd
-00000470 backcmd
-00000600 peek
-00000680 parseredirs
-000004a0 gettoken
-000011f0 malloc
-00000eab sleep
-00001a0c whitespace
-000001c0 fork1
-00000ae0 nulterminate
-00000e63 pipe
-00000ef3 getch
-00000160 getcmd
-00000ec3 write
-00000e83 fstat
-00000e73 kill
-00000e8b chdir
-00000970 parseline
-000001e0 runcmd
-00000a50 parseblock
-00000e7b exec
-00000e5b wait
-00001a04 symbols
-00000e6b read
-000007c0 parseexec
-00000ed3 unlink
-000001a0 panic
-00000e4b fork
-00000ea3 sbrk
-00000eb3 uptime
-00001a12 __bss_start
-00000cc0 memset
-00000000 main
-00000c30 strcmp
-00000f03 shutdown
-00000e93 dup
-000003f0 pipecmd
-000003a0 redircmd
-00000d90 stat
-00001a12 _edata
-00001a90 _end
-00000edb link
-00000e53 exit
-00000de0 atoi
-00000c90 strlen
-00000ebb open
-00000ce0 strchr
-00000ee3 mkdir
-00000eeb close
-00000430 listcmd
-00001160 free