Updates to OpenPGP best practices

When translating into spanish i noticed some issues with the OpenPGP Best Practices document. This will remove a wrong link in the document, fix some incosistences as GnuPG is an implementation for OpenPGP and it also will fix some typos. 
Why take this out? I realize some users will not actually verify the FP of the cert, but I think we should include the step for those who wish to do it.