Use matrix fill mode when filling the formulations

[guimarqu]

fix #406

Tests should pass when DynamicSparseArrays v0.3.0 released

[codecov]

Codecov Report

Merging #427 (331dd9c) into master (d894701) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #427   +/-   ##
=======================================
  Coverage   80.11%   80.12%           
=======================================
  Files          52       52           
  Lines        4204     4206    +2     
=======================================
+ Hits         3368     3370    +2     
  Misses        836      836           

Impacted Files	Coverage Δ
src/Algorithm/colgen.jl	95.88% <ø> (ø)
src/Coluna.jl	100.00% <ø> (ø)
src/MathProg/manager.jl	50.00% <ø> (ø)
src/optimize.jl	96.22% <ø> (ø)
src/MathProg/clone.jl	100.00% <100.00%> (ø)
src/decomposition.jl	97.97% <100.00%> (+0.03%)	⬆️

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