Extensions for Mixed-Integer Conic Models

[ccoffrin]

Juniper should be supporting MI-SDP now so this is a viable model to build and test. Start by getting the AbstractWRConicModel models working and then explore AbstractWRMModel. OTS seems like a reasonable candidate for testing.

[chriscoey]

https://github.com/chriscoey/MOIPajarito.jl also should work, but isn't registered yet (it may get moved into JuMP-dev when my thesis is done in May).
I'll probably add support for more MOI cones there, including a complex PSD cone (which works already in https://github.com/chriscoey/PajaritoExtras.jl, but that package is specific to Hypatia right now).