extend the default BrauerTableOp method

[ThomasBreuer]

• extended the default BrauerTableOp method to the case
  of cyclic defect such that all Brauer characters lift
  to characteristic zero (this case can be detected from the
  ordinary character table)

• extended the documentation accordingly

• extended the tests accordingly

[olexandr-konovalov]

Looks good to me (failed tests caused by the problem with Julia that should be fixed by #3131). You may wish to rebase it to have a clean pass, and look at two suggestions.

I was also wondering if GAP should have a PPart function. It has PValuation, but will it be better to use p^PValuation(n,p) instead of the loop that you use to calculate the ppart - I am not sure.

[olexandr-konovalov]

I suggest to remove quotes around p to ease reading.

[olexandr-konovalov]

@ThomasBreuer just to explain why: I read that first as p'-subgroup, then reread to figure out what does that mean. The style you use here is not consistent with other styles used in the GAP library: for example we have

grp.gi:      # compute generators for the torsion Omega p-subgroups of the center
grpprmcs.gi:##  O_p(G), the p-core of G, is the maximal normal p-subgroup
grpprmcs.gi:                        # abelian normal p-subgroup of G
grpprmcs.gi:    # p-subgroup of G; taking commutator subgroups, find abelian normal
grpprmcs.gi:    # p-subgroup of G.
grpprmcs.gi:    # p-subgroup; kernel is abelian p-group. Take image at this action, and

and also one case of

ctblsolv.gi:    # Choose a normal elementary abelian `p'-subgroup `N',

[codecov]

Codecov Report

Merging #3129 into master will increase coverage by <.01%.
The diff coverage is 92.1%.

@@            Coverage Diff             @@
##           master    #3129      +/-   ##
==========================================
+ Coverage   83.58%   83.59%   +<.01%     
==========================================
  Files         687      687              
  Lines      336919   336957      +38     
==========================================
+ Hits       281619   281671      +52     
+ Misses      55300    55286      -14

Impacted Files	Coverage Δ
lib/ctbl.gd	97.68% <ø> (ø)	⬆️
lib/ctbl.gi	79.01% <92.1%> (+0.54%)	⬆️
src/iostream.c	61.59% <0%> (-0.77%)	⬇️
src/stringobj.c	95.03% <0%> (+0.15%)	⬆️
hpcgap/lib/hpc/stdtasks.g	72.18% <0%> (+0.4%)	⬆️