Improve new wallet onboarding, especially for GPG keys
If Kleopatra is installed, add prompt to open it for generating a new GPG key if none are found. If Kleopatra is not installed, provide user with clear instructions to install Kleopatra, or to use gpg command to generate keys. Add reload button to list of GPG keys for after one is created.
This also sets Blowfish as the default selected option for encryption, and explicitly recommends it for inexperienced users. Reasons for such are outlined in !83 (comment 969132)