Update book example for GenericCharacterTables

[fingolfin]

This syncs it with the revised version in the book repo.

I've not tested this locally yet and will fix it up later today. So while I won't complain if someone wants to jump in and help out with any issues in here, please don't feel obliged. Ideally I'll complete this and then afterwards @benlorenz and @lkastner can have a final sanity check / point out anything I also should adjust.

I also plan to update https://github.com/oscar-system/book.oscar-system.org later. Let me know if there are other places that need to be adjusted.

[fingolfin]

Oops, there is a warning

WARNING: importing deprecated binding AbstractAlgebra.addeq! into GenericCharacterTables.
, use add! instead.

we'll take care of it.

@SoongNoonien can you please remove the addeq! import & replace the addeq! method? Something like this should do: replace

add!(x::GenericCyclo, y::GenericCyclo, z::GenericCyclo) = y+z

function addeq!(x::GenericCyclo, y::GenericCyclo)
	mergewith!(+, x.f, y.f)
	strip_zeros!(x.f)
	return x
end

by

function add!(x::GenericCyclo, y::GenericCyclo, z::GenericCyclo)
        if x !== y
		x.f = deepcopy(y.f)
	end
	mergewith!(+, x.f, z.f)
	strip_zeros!(x.f)
	return x
end

(untested, and I may have missed something else, so please double check it and ideally add a test case?)

[fingolfin]

Apparently there are deeper issues running this against Oscar master (it works against the latest Oscar release). We'll resolve this, too

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.68%. Comparing base (4a5b96d) to head (224a818).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4163      +/-   ##
==========================================
- Coverage   84.69%   84.68%   -0.02%     
==========================================
  Files         628      628              
  Lines       84449    84471      +22     
==========================================
+ Hits        71527    71535       +8     
- Misses      12922    12936      +14     

see 5 files with indirect coverage changes

[benlorenz]

Looks reasonable and seems to work fine.