Update solvers to MOI v0.9

[blegat]

Updates to do:

• Remove MOI.SingleVariable from the arguments of the @model macro.
• Implement MOI.DualObjectiveValue.
• Indices of MOI.SingleVariable constraints need to have the same index that the variable
• Implement MOI.Silent, MOI.SolveTime, MOI.RawStatusString, MOI.TimeLimitSec.
• Update the test script to follow the new guideline: http://www.juliaopt.org/MathOptInterface.jl/dev/apimanual/#Testing-guideline-1
• Add support for MOI.RawParameter.
• Rename MOIU.getconstant and MOI._constant to MOI.constant.
• Rename access to the resultindex field of MOI.ObjectiveValue to result_index.

For more details on what changed, see #737

List of solvers is taken from http://www.juliaopt.org/JuMP.jl/dev/installation/#Getting-Solvers-1:

• KNITRO.jl
• Cbc.jl Update to MOI v0.9 Cbc.jl#123
• CDCS.jl Updates to MOI v0.9 oxfordcontrol/CDCS.jl#1
• Clp.jl Update to MOI v0.9 Clp.jl#66
• COSMO.jl
• CPLEX.jl WIP: new CPLEX wrapper CPLEX.jl#261
• CSDP.jl Update to MOI v0.9 CSDP.jl#41
• ECOS.jl Updates to MOI v0.9 ECOS.jl#92
• Xpress.jl Moiv0.9 Xpress.jl#41
• GLPK.jl Re-write the MOI wrapper GLPK.jl#101
• Gurobi.jl Completely re-write the Gurobi MOI wrapper. Gurobi.jl#216
• Ipopt.jl Updates for MOI 0.9 Ipopt.jl#170
• Juniper.jl
• MosekTools.jl Update to MOI v0.9 MosekTools.jl#38
• OSQP.jl Update for MOI v0.9 osqp/OSQP.jl#55
• ProxSDP.jl MOI v0.9 again mariohsouto/ProxSDP.jl#58
• SCIP.jl Prepare for MOI v0.9 scipopt/SCIP.jl#126
• SCS.jl Updates to MOI v0.9 SCS.jl#144
• SDPA.jl Update to MOI v0.9 SDPA.jl#15
• SeDuMi.jl Updates to MOI v0.9 SeDuMi.jl#12

[rschwarz]

I think it would be good to merge #712 first. Right now, most MIP solvers will fail the Indicator tests, because the bridge is missing.

In SCIP, we have an implementation in a PR, but I think it would be cleaner to upgrade to MOI 0.9 first, then support Indicator constraints natively.

[mlubin]

GLPK, Ipopt, and SCS are the absolute minimum set of solvers needed to be ready before we tag MOI 0.9 so that we can run JuMP's examples under MOI 0.9.