Pulp deprecation warnings and CPSAT support

[Franco Peschiera]

I've recently added deprecation warnings for version 3.3 of pulp so that users can know island adapt their code to the new format that's coming on 4.0.

Also, I've added a cpsat API in the master branch so that users who implement a MIP can make use of that solver. There's no support for CP-like constraints but it should still be useful for pure integer problems and CPSAT relies on binary versions of most integer variables anyways.

I'll make the change to 4.0 as stable version in the next week's and then CPSAT will also be in pypi.

Best regards,

Franco 

PS: I'm curious of anyone on this chat heard of the recent purchase of NextMV by FICO. And of they have some opinion on the matter.