Create regression tests for import function

[irojkov-ph]

Feature Description

Currently, the checks that are made before any merge of a pull request and any release do not check if the data which were imported in PsPM using import functions were correctly imported, i.e. no missing data and no additional errors. That's why one needs to create a sort of procedure to test these import function properly. A way to do it is to implement a regression test and/or more diagnostic tests about the number of channels, markers, duration, etc.

P.S.: this feature request occured after I've pointed out this issue #136 .