Rename `MultirowChange` to `MultirowLinearChange`

[mohamed82008]

It seems useful to support changing quadratic terms so why not change this to linear?

[odow]

See also #142

[mohamed82008]

Interesting arguments there, but I am not suggesting removing "Multirow" just making it more clear, that is a "linear" change to each of the rows, just for clarity/verbosity.

[mohamed82008]

Is this a welcome change in a PR or should I close the issue?

[mlubin]

It's not clear that multirow change is even going to be used as it was intended for column generation. If we want to churn on this, we can just remove the modification instead.

[mohamed82008]

Hmm ok I will see if it is not used elsewhere, then I will make a PR to remove it to trigger more discussion.

[odow]

Closing since we're not going to change the name.