Declare is_one, is_zero as early as possible

[fingolfin]

Also export them explicitly (before @alias did it for us), and use @alias for
our LinearAlgebra aliases, too (makes it easier to find them by grepping)

CC @HechtiDerLachs this is what I was talking about

[fingolfin]

I've now updated this to also declare more aliases, taken from Nemo/Hecke/Oscar. The idea being that all of our packages should be able to freely and consistently use these aliases.

[thofma]

Makes sense

[codecov]

Codecov Report

Merging #1178 (bddb29c) into master (809bc71) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1178      +/-   ##
==========================================
- Coverage   85.02%   84.98%   -0.04%     
==========================================
  Files          97       97              
  Lines       26761    26761              
==========================================
- Hits        22753    22744       -9     
- Misses       4008     4017       +9     

Impacted Files	Coverage Δ
src/AbstractAlgebra.jl	50.42% <ø> (ø)
src/generic/PuiseuxSeries.jl	86.68% <0.00%> (-0.26%)	⬇️
src/generic/MPoly.jl	94.53% <0.00%> (-0.15%)	⬇️
src/Matrix.jl	91.58% <0.00%> (-0.13%)	⬇️
src/Poly.jl	92.16% <0.00%> (ø)
src/MatrixAlgebra.jl	92.71% <0.00%> (ø)
src/generic/RelSeries.jl	94.16% <0.00%> (ø)
src/generic/SparsePoly.jl	28.46% <0.00%> (+0.08%)	⬆️

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[fingolfin]

Tests are passing now (except for codecov coverage dropping minimally due to added code)