openpgp.encrypt, sign, encryptSessionKey, encryptKey and decryptKey now
return their result directly without wrapping it in a "result" object.
Also, remove the `detached` and `returnSessionKey` options of
openpgp.encrypt.
Keep supporting the old names as well though in `openpgp.generateKey`
and `getAlgorithmInfo`, but not in `openpgp.key.generate` (as it is
recommended that developers use `openpgp.generateKey` instead, and
it now throws when using `numBits` instead of `rsaBits`, so there's
no risk of silent key security downgrade).
The old names are now deprecated, and might be removed in v5.
