Simplify thanks for new API in CSDP

[blegat]

Simplification of the MOI wrapper thanks to coin-or/Csdp#12.
We play it safe now by considering most of CSDP internal data as a black box pointer so this PR should fix #39 and #40

[coveralls]

Coverage decreased (-18.2%) to 46.837% when pulling 8f63bbf on bl/refactor into e367784 on master.

[codecov-io]

Codecov Report

Merging #48 into master will decrease coverage by 15.8%.
The diff coverage is 73.13%.

@@             Coverage Diff             @@
##           master      #48       +/-   ##
===========================================
- Coverage   70.55%   54.75%   -15.81%     
===========================================
  Files          10       10               
  Lines         557      652       +95     
===========================================
- Hits          393      357       -36     
- Misses        164      295      +131

Impacted Files	Coverage Δ
src/CSDP.jl	100% <ø> (ø)	⬆️
src/blockmat.h.jl	72.72% <ø> (ø)	⬆️
src/blockmat.jl	60.62% <100%> (-22.05%)	⬇️
src/declarations.h.jl	19.84% <58.62%> (-24.82%)	⬇️
src/declarations.jl	38.88% <59.25%> (-58.99%)	⬇️
src/MPB_wrapper.jl	66.17% <75.75%> (+4.47%)	⬆️
src/MOI_wrapper.jl	76.96% <87.8%> (-0.01%)	⬇️
src/options.jl	44.44% <0%> (-55.56%)	⬇️
... and 1 more

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