candelete is inconsistent with canget

[mlubin]

We would probably like to pass in the type of the index instead of the index value itself.

[blegat]

There might be cases where some variables can be deleted and some cannot. For instance, a solver could say that a variable cannot be deleted if it still appears in some constraints

[mlubin]

That sounds like it could also just be an error on delete!. Unclear though...

[blegat]

There is the same performance issue in CachingOptimizer for deleting constraints so I think we should go for it

[odow]

Bump. I just encountered this.