Remove need for __construct in EncryptorInterface

[slootjes]

The __construct in the interface now takes away the freedom to implement your own encryptor which does more than just using a key. I want to create a asymmetrical encryptable class where I need to pass services to the __construct. It would be better if the encryptor was set as a service and then passed as a whole instead of initializing the encryptor and passing the key in the service.

[ambta]

Hi Slootjes,

This will be included in the next version.
Thanks for your feedback!