prerelease notes for 0.19-alpha

[mlubin]

After merging this I'll tag v0.19-alpha. I'm not certain that add JuMP#v0.19-alpha will work though.

@blegat @odow @joaquimg @joehuchette @juan-pablo-vielma @IssamT

Please take a look and check that you agree with the lists of breaking changes/new features/known issues.

[joehuchette]

LGTM

[joehuchette]

duplicated "and quadratic"

[blegat]

Also duplicated "the"

[joehuchette]

Nit: End with period (here and below).

[codecov]

Codecov Report

Merging #1523 into master will increase coverage by 0.1%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #1523     +/-   ##
=========================================
+ Coverage   89.47%   89.58%   +0.1%     
=========================================
  Files          27       27             
  Lines        3621     3736    +115     
=========================================
+ Hits         3240     3347    +107     
- Misses        381      389      +8

Impacted Files	Coverage Δ
src/quad_expr.jl	87.95% <0%> (-1.93%)	⬇️
src/JuMP.jl	75.67% <0%> (-0.52%)	⬇️
src/nlp.jl	90.55% <0%> (+0.06%)	⬆️
src/variables.jl	93.45% <0%> (+0.11%)	⬆️
src/aff_expr.jl	93.16% <0%> (+0.24%)	⬆️
src/macros.jl	88.46% <0%> (+1.26%)	⬆️

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[blegat]

We could also mention that atm there is no automatic bridging between soc and quadratic while there was the conic <-> lpqp bridges with mpb but there are open prs for that

We could also advertise that JuMP extensibility has been improved as MOI is now extensible by design and JuMP macros are now extensible and a doc is coming

[mlubin]

We could also mention that atm there is no automatic bridging between soc and quadratic while there was the conic <-> lpqp bridges with mpb but there are open prs for that

Is this a known issue or a breaking change (that it doesn't work anymore)?

[blegat]

Is this a known issue or a breaking change (that it doesn't work anymore)?

Not sure which yet. For quadratic to SOC, jump-dev/MathOptInterface.jl#483 does the non-homogeneous tranformation but I am not sure that the homogeneous one (i.e. x^2 + y^2 <= z^2) will be done for JuMP v0.19. For the SOC to quadratic, we are not sure to do it anymore because it would also work for NLP solvers: jump-dev/MathOptInterface.jl#478 (comment)