Accommodate correctly pluralized ViewStrings in GAP

[wilfwilson]

In some hopefully future version of GAP, some nouns will be correctly pluralised to match their number. For example, <pc group of size 3 with 1 generators> will become <pc group of size 3 with 1 generator>.

The changes in this PR maintain the backwards and forwards compatibility of this package with GAP.

See gap-system/gap#3992 and gap-system/gap#4050 if you want more context.

[codecov[bot]]

Codecov Report

Merging #33 into master will decrease coverage by 0.78%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
- Coverage   90.88%   90.10%   -0.79%     
==========================================
  Files          22       22              
  Lines        2458     2364      -94     
==========================================
- Hits         2234     2130     -104     
- Misses        224      234      +10     

Impacted Files	Coverage Δ
gap/walrus.gd	100.00% <ø> (ø)
gap/pregroupoffreegroup.gi	84.21% <0.00%> (-4.75%)	:arrow_down:
gap/location.gi	93.75% <0.00%> (-2.48%)	:arrow_down:
gap/examples.gi	65.90% <0.00%> (-2.09%)	:arrow_down:
gap/relator.gi	91.66% <0.00%> (-1.67%)	:arrow_down:
gap/pregroup.gi	81.34% <0.00%> (-1.40%)	:arrow_down:
gap/presentation.gi	93.26% <0.00%> (-0.88%)	:arrow_down:
gap/util.gi	91.66% <0.00%> (-0.34%)	:arrow_down:
gap/place.gi	93.02% <0.00%> (-0.21%)	:arrow_down:
gap/walrus.gi	95.48% <0.00%> (-0.08%)	:arrow_down:
... and 5 more