Add extraspecial_group and is_extraspecial_group

[ThomasBreuer]

• add extraspecial_group
• add is_extraspecial_group, add it to the list of general group properties in the manual
• add is_dicyclic_group and is_dihedral_group to the list of general group properties in the manual
• sort the general group properties in the manual alphabetically

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.88%. Comparing base (13b473d) to head (b42730e).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4999      +/-   ##
==========================================
- Coverage   84.89%   84.88%   -0.01%     
==========================================
  Files         697      697              
  Lines       93897    93918      +21     
==========================================
+ Hits        79711    79724      +13     
- Misses      14186    14194       +8     

Files with missing lines	Coverage Δ
src/GAP/wrappers.jl	95.37% <100.00%> (+0.02%)	⬆️
src/Groups/group_constructors.jl	94.20% <100.00%> (+0.55%)	⬆️

... and 2 files with indirect coverage changes

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