Changes in direct sums construction

[StevellM]

We try here to suggest a consistent patterns for direct sums/direct products/biproducts for some objects which abstractly have biproducts. The general idea is:

Those objects have finite direct sums and finite direct products which agree, and which are called biproducts. We leave as an interface to the user the following choices:

• construct the biproduct as a direct_sum and only get as extra output the injection maps;
• construct the biproduct as a direct_product and only get as extra output the projection maps;
• construct the biproduct as a biproduct and return the injection maps as well as the projection maps.

Moreover, for the objects with "orthogonality relations" i.e. AbstractLat, AbstractSpace and TorQuadModule, we get rid of orthogonal_sum since this was misleadingly a direct_sum in disguise.

For consistency, we rename anything in this context named orthogonal_sum as direct_sum.

We also provide for TorQuadModule a normal sum +, similarly to what is possible for ZLat, whenever it makes sense (this could be seen as an "inner sum")

[thofma]

Needs rebase

[codecov]

Codecov Report

Patch coverage: 92.90% and project coverage change: +0.05 🎉

Comparison is base (22d78b5) 74.17% compared to head (1d82f9e) 74.22%.

❗ Current head 1d82f9e differs from pull request most recent head 3359654. Consider uploading reports for the commit 3359654 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #985      +/-   ##
==========================================
+ Coverage   74.17%   74.22%   +0.05%     
==========================================
  Files         347      347              
  Lines      110707   110696      -11     
==========================================
+ Hits        82117    82169      +52     
+ Misses      28590    28527      -63     

Impacted Files	Coverage Δ
src/Deprecations.jl	4.54% <ø> (ø)
src/GrpAb/GrpAbFinGen.jl	75.16% <85.71%> (+0.70%)	⬆️
src/QuadForm/Quad/ZLattices.jl	94.13% <87.50%> (-0.55%)	⬇️
src/QuadForm/Quad/Genus.jl	93.82% <90.00%> (ø)
src/QuadForm/Quad/Spaces.jl	83.20% <90.00%> (+0.07%)	⬆️
src/QuadForm/Torsion.jl	90.70% <90.00%> (-0.43%)	⬇️
src/QuadForm/Herm/Genus.jl	92.71% <100.00%> (ø)
src/QuadForm/Lattices.jl	86.47% <100.00%> (+0.20%)	⬆️
src/QuadForm/Quad/ZGenus.jl	97.77% <100.00%> (+0.06%)	⬆️
src/QuadForm/Spaces.jl	94.46% <100.00%> (+0.01%)	⬆️
... and 34 more

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[thofma]

Is the :task kept for backwards compatibility?

[thofma]

P.S.: Also documentation build is failing.