RT2119,3407: Updated to dgst.pod

Re-order algorithm list.
Be consistent in command synopsis.
Add content about signing.
Add EXAMPLE section
Add some missing options: -r, -fips-fingerprint -non-fips-allow
Various other fixes.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(cherry picked from commit 6aa9dbab0f9b90060b7ee609b8c3c726ce4faf21)
Add tags/TAGS

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 9d6253cfd3395dfe7147dae134579c6b16544c53)