Optional *_aslcontext.json files
- Make the creation of *_aslcontext.json files optional.
- This is facilitated by the addition of two (mutually exclusive) flags to the `d2b run` command (specifically, `--[no-]include-aslcontext-json`). The "no" flag is taken to be the default if neither is specified, that is, no *_aslcontext.json files will be produced, regardless of whether of not asl data is found in the dataset.
- **NOTE:** These JSON files seem to cause errors in the bids-validator (v1.8.0), however, these files are listed in the spec, is this a bug in the validator?