Robust essential cut (lazy constraint) generation

[guimarqu]

Essential cut gen is performed :

• in the cut callback algorithm
• each time the colgen algorithm finds an integer solution
• after heuristic

for colgen : when the cut violates the solution, the colgen restarts at phase 3 if it was at phase 3 and at phase 1 if it was at phase 1 or 2

fix #450

[codecov]

Codecov Report

Merging #452 (b2c19c0) into master (7265c97) will increase coverage by 0.09%.
The diff coverage is 94.52%.

@@            Coverage Diff             @@
##           master     #452      +/-   ##
==========================================
+ Coverage   80.71%   80.81%   +0.09%     
==========================================
  Files          51       51              
  Lines        4310     4347      +37     
==========================================
+ Hits         3479     3513      +34     
- Misses        831      834       +3     

Impacted Files	Coverage Δ
src/MOIcallbacks.jl	94.23% <83.33%> (+0.61%)	⬆️
src/Algorithm/colgen.jl	96.74% <93.10%> (+0.10%)	⬆️
src/Algorithm/basic/cutcallback.jl	97.14% <95.23%> (+0.84%)	⬆️
src/Algorithm/conquer.jl	82.07% <100.00%> (+2.28%)	⬆️
src/Algorithm/branching/branchinggroup.jl	86.51% <0.00%> (-1.13%)	⬇️
src/Algorithm/branching/branchingalgo.jl	90.75% <0.00%> (-0.85%)	⬇️
src/Algorithm/storage.jl	73.77% <0.00%> (-0.82%)	⬇️
src/decomposition.jl	98.50% <0.00%> (-0.01%)	⬇️

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[guimarqu]

I think it's wrong, it should restart at phase 2 in colgen because it never does essential cutgen at phase 1. I'll fix tomorrow.