Subject ID in Single Subject module

[MontrealSergiy]

Subject ID (that is Participant Label) is mandatory field , which is automatically setup on task submission when argument is BidsSjubject.

However some things can confuse user

1. Even for single BidsSubject file collection, user have to look at another parameter to to understand that computer will fill it (actually overwrite.)

So some explanation is required in Subject ID field (rather than BIDS Dataset Folder). And it is best to clearly explain that data will be overwritten.

If case is unambitious Subject ID can even be populated immediately at task setup.

2. If cbsvv file list is supplied user cannot leave the field is blank, but cannot enter all the subject ids either due to prohibited space
   So this field should not have space validation

To reproduce

1. Create BidsSubject list in cbrain
2. Create task with that Cbrain list Submit to MiDeface
3. Try to not fill Subject ID files, say sub-01 and sub-02
4. Observe error "mandatory parameter is missing"
5. Try to supply value "01 02"
6. Observe error "invalid character"

This is confusing for most user. An experienced users might guess that any dummy value

As workaround new pipelines could relax string validation.

[prioux]

I adjusted the description for issue 1. See 9c2f117

I don't understand issue 2. Can you please provide an example user story where the problem occur?

[MontrealSergiy]

I refined the text