Change the data parameter of encrypt_data from &str to &[u8]

[Istvan91]

While it is recommended to use ascii as the password, this is "only" a recommendation. Furthemore encryption is not only used by the standard Attribute "User-Password", but by some Vendor Specific Attributes.

To make the encrypt utility function more versatile it would be great to change the &str parameter to &[u8] (which would be a breaking change imho).

The enforcement of ascii/non-ascii should be done at a higher application level.

[MikhailMS]

Sounds like a great thing to resolve, thank you for pointing that out (didn't know that some vendor specific attr also using encryption)

Would review it asap :)

[MikhailMS]

It is done on dev locally, so should be bundled into next release (0.4.0, since we got a breaking(in a way) change)