Add pkg/JuliaInterface/gap/override.g

[fingolfin]

... and merge various overrides in there.

[codecov]

Codecov Report

Attention: Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 74.50%. Comparing base (17b5967) to head (794f3a7).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/JuliaInterface/gap/override.g	80.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1159      +/-   ##
==========================================
- Coverage   74.51%   74.50%   -0.02%     
==========================================
  Files          55       55              
  Lines        4713     4711       -2     
==========================================
- Hits         3512     3510       -2     
  Misses       1201     1201              

Files with missing lines	Coverage Δ
pkg/JuliaInterface/read.g	100.00% <100.00%> (+12.00%)	⬆️
src/GAP.jl	86.88% <ø> (-0.22%)	⬇️
pkg/JuliaInterface/gap/override.g	80.00% <80.00%> (ø)

... and 1 file with indirect coverage changes