Added Option for External Password Manager
Added option to have passwords be managed by an external tool like tpm instead of relying on gnome-keyring. This feature requires explicit activation and for the user to set the name of the external password manager which must support insert and show arguments and read/write to stdin/out. Also servers that require login, will now re-login when it detects the session's authentication has expired which cannot be reliably inferred from the session cookie.
Also allow Komikku to run if a server isn't supported like if testing an older version or going back from a feature branch
Close #70