[datetime] Improve I/O support for time of acquisition

[Edouard2laire]

This PR is here add support of datetime information from various files :

** EDF**

• Import/export date from the file
• Fix export issue https://neuroimage.usc.edu/forums/t/flat-lines-in-stellate-after-edf-export-from-brainstorm/54612/9
• Improve performance to find the max of the file (use larger block size than 1 seconds)

For the performance, exporting a 2-hour file (34 channels at 250Hz) reduced the time to find the max values from 24 seconds to 1 second. (nblock is decreasing from 7681 to 5)

** SNIRF**

• modify the reader / writter to support datetime information (according to snirf standard)

** BIDS **

• Read from scan.tsv

** FIF **

Read from the file. Note, i tried on a file from https://openneuro.org/datasets/ds000117/versions/1.1.0 but i find the following acquisition date: '1941-56-26'T'09:04:09' i don't think it's right but it make sense based on the information in the file. I guess the date is wrong but time is ok ? not sure.