Documentation - Solver Status Symbol

[ccoffrin]

These documentation pages do not clearly indicate what the semantics of the standard solver status symbols are for these classes of solvers,

https://github.com/JuliaOpt/MathProgBase.jl/blob/master/doc/lpqcqp.rst
https://github.com/JuliaOpt/MathProgBase.jl/blob/master/doc/conic.rst
https://github.com/JuliaOpt/MathProgBase.jl/blob/master/doc/nlp.rst

[mlubin]

The (limited) documentation for the status symbols is at http://mathprogbasejl.readthedocs.io/en/latest/solverinterface.html#status. It's uniform across all classes of solvers.

[mlubin]

Closing in favor of #164