Refactors decrypt() and uses crypto functionality from rc_openpgpjs.crypto.js

Throws out a lot of bloat from decrypt() and creates processReceived() as replacement

Refactors encryptAndSign() and shoves public key info box into separate function

Nukes encryptAndSend(). Ohh, encryptAndSend(). I knew you were trouble when you walked in, now you're lying on the cold hard ground. OOOOOH! AAAAH! OOOH!!! AAH!!! TROUBLE, TROUBLE, TROUBLE!!!

Also disables email signing for now, it appears as if OpenPGP.js has
broken it in some release. Saving for later.

TODO: Shove old passphrase verification checks from decrypt() into
set_passphrase()