Accommodate correctly pluralized ViewStrings in GAP

[wilfwilson]

In a future version of GAP, some nouns will be correctly pluralised to match their number. For example, the ViewString for CyclicGroup(3); will change from <pc group of size 3 with 1 generators> to <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 for more context.

[codecov[bot]]

Codecov Report

Merging #85 into master will decrease coverage by 0.01%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
- Coverage   83.45%   83.43%   -0.02%     
==========================================
  Files          11       11              
  Lines        5193     5193              
==========================================
- Hits         4334     4333       -1     
- Misses        859      860       +1     

Impacted Files	Coverage Δ
lib/main.gi	80.95% <0.00%> (-0.08%)	:arrow_down:

[olexandr-konovalov]

@wilfwilson thanks!