suggestion to match the newer version of windef from openpiv 0.24.0

[alexlib]

Following user's request for the windef to work with the sequential data, we adopted your format of sequencing: '(1+2),(3+4)' and so on and made it a part of the openpiv.tools.MultiProcesser:

see here https://github.com/OpenPIV/openpiv-python/blob/e3b185987a729381655d341cc7b358796d846314/openpiv/tools.py#L407

we of course updated documentation - see here:
https://openpiv.readthedocs.io/en/latest/src/windef.html

However, this might interfere with the Tk GUI part (not sure about it).

In any case, please run tests vs 0.24.0 and see if it makes sense to unify this code once in the library and not in the GUI. Of course, it can be just a meaningless work, cause we're still in beta and not finalized the formats.