Methods for setting API tokens use getpass
    
    The methods `set-distgit-token`, `set-pagure-token` originally
    accepted a token as a command-line argument and this wasn't a sane
    approach. Now the token is safely put via getpass method.
    Also the code was moved to a shared place in rpkg because other
    tool uses it too.
    
    Fixes: rhbz#2089694
    JIRA: RHELCMP-13435
    
    Signed-off-by: Ondřej Nosek <onosek@redhat.com>