feat: support receiving a new account via otpauth:// URI from the commandline in the UI

This change implements necessary control flow to pick up on accounts being passed to Keysmith via commandline options.

This change covers UX only for the happy flow case in which the received account is a valid otpauth:// URI.
If such an URI is passed to Keysmith, then the Add Account form is automatically pushed on the page stack and pre-populated with data received from the commandline.
With this UX, if the account is valid the user may either accept it immediately or tweak settings (most likely account name/issuer) to make it valid.

Issues: #7, #14