Simplify, reformat, and modernize.

The user-facing changes, some of which required a PORTREVISION bump:

• Don't make everybody download the signature file
• Add USES=readline, rather than making assumptions about it being in /usr. A side effect of this was that gnupg was being built with readline support on 10 but not 11, except when LDAP was enabled which brought it in as a side effect
• Don't make manpages dependent upon the DOCS option. As a side effect, everybody now gets the info files. Also, put the help files into DOCSDIR instead of DATADIR; best as I can tell they aren't being called from within gpg
• Reword the pkg-descr to describe what gpg is, rather than making a frightening-sounding statement about patents and unrestricted use
• Handle the gpg symlink in the plist, and be a little looser about creating it and tighter about removing it
• Remove the pkg-message. The pinentry dependency installs a pinentry dialogue already