create automatic check to make sure that block length and IBI are multiples of the TR

[Remi-Gau]

I think we should add an automatic check for this that send an error in case we don't the math wrong.

Originally posted by @Remi-Gau in #25

[marcobarilari]

related to #29

[Remi-Gau]

related to PR #41 and issue #40

technically if the experiment is paced by the triggers then we do not need to check this: this would make this issue obsolete

[marcobarilari]

agree, from my side this can be closed