'only' constructors with TwiceDifferentiableHv

[tlienart]

This is in view of https://github.com/JuliaNLSolvers/Optim.jl/issues/738 @pkofod

• add only_fg_and_hv for a constructor where only these two things are provided
• add only_fghv for a constructor that looks like only_fgh and allows re-using computations for the construction of Hv (a common trick using the construction of the gradient to get Hv, see issue quoted above).

This may break Optim in that the call to fg is now the "standard" format used elsewhere IE: (f, g, x) instead of just (g, x); I'll open a PR for Optim soon too.

PS: failure on nightly are due to the project toml not being up to date, see PR #108

Edit marked as "do not merge" for now, the ambiguity of calling convention for fg either with (g, x) or (f, g, x) is causing me some trouble now ok, see also https://github.com/JuliaNLSolvers/Optim.jl/pull/742

[codecov[bot]]

Codecov Report

Merging #109 into master will increase coverage by 0.13%. The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #109      +/-   ##
=========================================
+ Coverage   93.46%   93.6%   +0.13%     
=========================================
  Files          10      10              
  Lines         490     500      +10     
=========================================
+ Hits          458     468      +10     
  Misses         32      32

Impacted Files	Coverage Δ
src/NLSolversBase.jl	80% <ø> (ø)	:arrow_up:
src/objective_types/twicedifferentiablehv.jl	100% <100%> (ø)	:arrow_up:
src/objective_types/incomplete.jl	98% <100%> (+0.32%)	:arrow_up:

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[pkofod]

Welcome to the frightening world of NLSolversBase :) I will have a look as soon as possible. Thanks

[tlienart]

bump?

[pkofod]

Great, looks good! Sorry for the long wait.