Refactor check_and_format_names() #598
Description
Currently check_and_format_names() is used to format names (e.g. add missing "sub-" or "ses-" prefixes, expand the @TO@ flag) for folder creation, but is also used in data_transfer.py. However, the check in data transfers was leading to problems when new keys are added (#510) or changes in validation (#575), on which the validation feature was turned off. It is not really necessary to perform this validation during transfer, only in folder creation.
Therefore, this bloated function can be stripped down, using only format_names in transfer.