Wildcard in channel selections for spectra

[leemundy]

Feature description
In a command like:
ta.baseline(degree=2,exclude=[(1000,3000),(5000,7000),(8500,11000)],remove=True)
You do not quickly know the first or last point in a spectrum so it would be more
convenient if there was a wildcard ability. For example,
ta.baseline(degree=2,exclude=[(,3000),(5000,7000),(8500,)],remove=True)
ta.baseline(degree=2,exclude=[(,3000),(5000,7000),(8500,)],remove=True)
Perhaps this exists but I do not know what to put to indicate -- take all channel
beyond or below a number.

Solution
If you have an idea of how to solve the problem, please describe it!

Additional context
Simplies user interaction, especially in frequency switched spectra where the area of most interest
is just the overlap region between the two negative images.

[teuben]

I'd proposed there be an include=[(3000,5000),(7000,8500)] for this kind of case.

[teuben]

an include= was added to our Spectrum.baseline which turns an include= into exclude= and passes this on to the next baseline routine. However, for now this only works in channel space, since attaching units to baseline selection is broken, see #260