enforce message signing when encrypting

[tomholub]

.

[tomholub]

Here

there are the following methods currently possible:

1. unprotected
2. sign only
3. encrypt only
4. encrypt and sign

I would like to forbid option 3 in the UI.

The easiest implementation could be:

• on "sign" clicking, always set sign to true regardless of previous state if "encrypt" is selected
• on "encrypt" clicking, if user is enabling "encrypt", it should also auto-enable "sign"

Should be covered with UI tests too. We have a test method available for setting these toggles.