Better error handling

[bkushigian]

Currently I have stuff like

    if len(board) != 3:
        print(
            f"\033[31;1mBoard {board} is not a valid board for aggregation. Expected 3 cards, got {len(board)}\033[0m"
        )
        print(
            "If you require aggregation for turn boards, please contact the developers and file a feature request."
        )
        sys.exit(-1)

inside of pious.pio.aggregate::aggregate_single_file and this should be an exception. A direct call to sys.exit should be placed in the CLI wrapper.

I should go through and replace any sort of error printing/exit type stuff with exceptions, possibly w/ special message encodings that can be printed by a CLI.