Check the order of command line arguments and give helpful error message.

I tried this command:

F:\GitHub\silnlp>poetry run python -m silnlp.nmt.translate --memory-growth --clearml-queue langtech_40gb --src-project GELA3_2022_12_12 --books OT BT-English-NLLB\experiment

And there was this error message:

2022-12-15 14:31:47,439 - silnlp.common.environment - INFO - Using workspace: S: as per environment variable SIL_NLP_DATA_PATH.
usage: translate.py [-h] [--memory-growth] [--checkpoint CHECKPOINT] [--src SRC] [--trg TRG] [--src-prefix SRC_PREFIX] [--trg-prefix TRG_PREFIX] [--start-seq START_SEQ] [--end-seq END_SEQ]
                    [--src-project SRC_PROJECT] [--books books [books ...]] [--src-iso SRC_ISO] [--trg-iso TRG_ISO] [--output-usfm OUTPUT_USFM] [--eager-execution] [--clearml-queue CLEARML_QUEUE]
                    experiment
translate.py: error: the following arguments are required: experiment

I think this is because the --books parameter is a list option and so the experiment is included as a book to be translated.
Could we check for the order of the arguments and provide an error message that explains the problem, or better still checks to see whether the last book is actually an experiment?

Start by reproducing the command through the silnlp.nmt.translate entry point and inspect how the --books list and required experiment argument are parsed. Confirm the reported ordering failure, then add validation or an error message that explains the conflict and verify that valid translations still work.