Memory leakage during optimization

[SNMS95]

It seems there is come memory leakage somewhere. It can be clearly seen if the topopt example is run and you monitor the memory. It is steadily increasing. This results in OOM-KILL events on HPCs.

1. Part of the reason is not destroying the PETSc objects. This is easily fixed.
2. We need some tool to do this everytime we make changes [Scalene perhaps?]
3. There is another source that I have not been able to pinpoint yet