New features: private-key passphrase support, .wskprops overwrite confirmation

For the console and jwt-auth commands, a --passphrase flag was added for you to specify a passphrase for your private-key if it is passphrase protected.

For the console:select-integration command, an interactive confirmation is presented to the user for overwriting the .wskprops file. An --overwrite flag can be set to bypass the prompt, to always overwrite the .wskprops file.