Fix primal solution check

[guimarqu]

Fix #146
Make some methods of AbstractSolution more generic

[codecov-io]

Codecov Report

Merging #148 into master will decrease coverage by 0.05%.
The diff coverage is 54.54%.

@@            Coverage Diff             @@
##           master     #148      +/-   ##
==========================================
- Coverage   76.32%   76.26%   -0.06%     
==========================================
  Files          37       37              
  Lines        1812     1816       +4     
==========================================
+ Hits         1383     1385       +2     
- Misses        429      431       +2

Impacted Files	Coverage Δ
src/incumbents.jl	80% <ø> (ø)	⬆️
src/algorithms/colgen.jl	94.77% <100%> (ø)	⬆️
src/solsandbounds.jl	83.52% <50%> (-1.66%)	⬇️

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