copy files from APG to support APG's ENCRYPT* Intents
gnupg-for-java: also allow fetching secret keys using GnuPGKey contructor

Before, it would only search and return public keys
gnupg-for-java: allow fetching secret keys using GnuPGContext.getKeyByFingerprint()
REBASE into 'gnupg-for-java: also allow fetching secret keys using GnuPGKey contructor'
gnupg-for-java: add listSecretKeys() and searchSecretKeys() to GnuPGContext
make APG's SELECT_SECRET_KEY Intent only show secret keys