Add support for cbv and phase sufixes for func files

[Remi-Gau]

Also we only support bold as contrast label for now and cbv and phase are also in the specs.

This seems more of an edge case at the moment and might require more coding that could be rendered moot when we have a schema to help us. So I would suggest that we open an issue for this point (to remind ourselves and let others know we know) but do not move on to fix it right away.

Originally posted by @Remi-Gau in #99 (comment)