add option to also print warning message to screen

warnings are now 'silent' in the sense that they only appear in log files, not in the terminal output, which is wrong

switching to verbose warnings directly would be too painful for now, given all the deprecated stuff that is still being triggered and should be fleshed out first

for now, we can provide the possibility for verbose warnings using a `print_to_screen` named argument, which can later be switched to default `True`