adding an option to check Protocol_Translator.json

[sarahoh]

It would be nice to include an option that tells bidskit perform some checks to make sure that the Protocol_Translator.json file is compatible with BIDS naming rules.

For example:

1. checking that the final suffix is allowed (not deprecated or otherwise nonstandard) according to BIDS.
2. checking that the key-value pairs appear in the order desired by BIDS
3. checking that there are no leading zeroes in run numbers (this may already be taken care of)

Thanks so much!