added a skeleton "create key" UI that automatically gets name and email

The context menus should be handled by Fragments, that's not sorted out
yet.  Currently the menus pop up, but don't do anything.  Also, this is not
yet wired up to actually create a key.
gnupg-for-java: add simple method for generating a new PGP key
REBASE into ''    added a skeleton "create key" UI that automatically gets name and email
REBASE into     add craziness to allow file associations for .gpg .pgp .asc and .sig #1455
run key generation in an AsyncTask with a ProgressDialog

It currently grabs the Name, Email, Comment, Key size/lenght, and expire
date from the CreateKeyActivity fields.  CreateKeyActivity needs to have
subkey handling, something like APG/OpenPGP Keychain but we sensible
defaults.