more doc fixes

dgst: using digest instead of specific digest commands
the digest list specified in man dgst may be inaccurate, hence using
digest and referring to the list in digest-commands

'sha' as a digest name is no longer supported

dgst,pkeyutl cmds help cleanup
- In dgst, pkeyutl cmds, some options help was missing.
- fixed a minor typo in openssl.pod, that fixes make install.
- digest-commands was showing ‘sha’, which is not a supported digest
anymore.

Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>

apps/progs.h

@@ -214,7 +214,6 @@ static FUNCTION functions[] = {
 #ifndef OPENSSL_NO_MD_GHOST94
     { FT_md, "md_ghost94", dgst_main},
 #endif
-    { FT_md, "sha", dgst_main},
     { FT_md, "sha1", dgst_main},
     { FT_md, "sha224", dgst_main},
     { FT_md, "sha256", dgst_main},