Add hash command

[vinc]

Add a hash command to compute the SHA256 digest of a file.

By default it'll only show half of the digest (same width as MD5) because the VGA screen is only 80 chars long.

/tmp
> hash /tmp/lisp/*.lsp
CC96B368B747E0C1988D96BFE4DF6527 /tmp/lisp/colors.lsp
5BA4E29B643AFE102D136786D1148FB4 /tmp/lisp/factorial.lsp
61E20049870E053CA52AC878ED063C9C /tmp/lisp/fetch.lsp
9C075B38308B785539D7052100250663 /tmp/lisp/fibonacci.lsp
4337A80396D3E6CCA664D61A95361E67 /tmp/lisp/geotime.lsp
9C0DD640E8DC34C04BA925906F71D911 /tmp/lisp/ntp.lsp
B9C1239245B00DD89CEA35334511CC2C /tmp/lisp/pi.lsp
589CBBC31EB7B2C521A4D66CA4506201 /tmp/lisp/sum.lsp

/tmp
> hash lisp/*.lsp
CC96B368B747E0C1988D96BFE4DF6527 lisp/colors.lsp
5BA4E29B643AFE102D136786D1148FB4 lisp/factorial.lsp
61E20049870E053CA52AC878ED063C9C lisp/fetch.lsp
9C075B38308B785539D7052100250663 lisp/fibonacci.lsp
4337A80396D3E6CCA664D61A95361E67 lisp/geotime.lsp
9C0DD640E8DC34C04BA925906F71D911 lisp/ntp.lsp
B9C1239245B00DD89CEA35334511CC2C lisp/pi.lsp
589CBBC31EB7B2C521A4D66CA4506201 lisp/sum.lsp

/tmp
> hash *.txt
6DFD0C65EE6CAE71124406A3126D10BD alice.txt
E04EFE3389B3A36BE5FF6D80A486BBA7 machines.txt

/tmp
> hash *.txt --full
6DFD0C65EE6CAE71124406A3126D10BD4D563858A51C5404D9E82194390D8767 alice.txt
E04EFE3389B3A36BE5FF6D80A486BBA76681686A2956A59A7CEB5440439DD548 machines.txt

[vinc]

Screenshot showing the colored output: