Allow INFEASIBLE_OR_UNBOUNDED and add raw_status

[blegat]

This is useful for SDPA which often returns this status.

[coveralls]

Coverage decreased (-0.06%) to 50.289% when pulling a76dd30 on bl/inf_or_unbd into 61c8737 on master.

[coveralls]

Coverage decreased (-0.06%) to 50.289% when pulling a76dd30 on bl/inf_or_unbd into 61c8737 on master.

[codecov]

Codecov Report

Merging #10 into master will decrease coverage by 0.07%.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##           master      #10      +/-   ##
==========================================
- Coverage   54.53%   54.46%   -0.08%     
==========================================
  Files          20       20              
  Lines        1003     1008       +5     
==========================================
+ Hits          547      549       +2     
- Misses        456      459       +3

Impacted Files	Coverage Δ
src/sos.jl	73.84% <66.66%> (-0.76%)	⬇️
src/invariant.jl	65.74% <80%> (-0.62%)	⬇️

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