[SNIRF]] Fix data importation

[Edouard2laire]

Improve snirf file reading. This is a smaller version of #756 for easier review

• Read file where timeOffset is not defined in the aux structure
• Fix the channel names when using custom name (replace Tx with S and Rx with D)

[Edouard2laire]

@rcassani, we are hosting a workshop at Concordia next week. Do you think you could merge this PR before Thursday as it is needed to load the dataset we want to show to the participants?

Thanks a lot :)

[rcassani]

@Edouard2laire , done
FYI @tmedani

[tmedani]

Thanks @rcassani
@Edouard2laire, it will be great to add it to the list of the courses in the website,
and we can post announcement on the LinkedIn as well

[Edouard2laire]

Thanks a lot.

You can find all the information about the workshop here: https://www.artinis.com/nirs-introduction-course-ca