Optimization Process Blocking UI

[NicerNewerCar]

An issue originally posted by @amymmorton on the behalf of Melaine Baker in #117 (comment)

When I tried to track the volume of the wrist, once I clicked ok in the
tracking dialog menu, the program would freeze and give an "Not responding"
error message at the top of the window. This window would close itself, then
I would hit "Tracking Dialog" in Autoscoper to try again and ran into the
same error. I closed the interface all together and redid the volume
realignment, clicked "Tracking Dialog", set up the tracking options, hit ok,
and ran into the same error. I also tried again several hours later and still
was getting a "Not responding" message.

This issue is caused by the optimization process blocking the UI process while it is running.

[NicerNewerCar]

This issue was not caused by process blocking as initially assumed, see PR #148 for more details.

[amymmorton]

Can we allow for an interrupt/ abort of the optimization?

As in #148 comments - if the wrong frame window was entered- there's nothing to do but wait-

[NicerNewerCar]

Yup, we need to be able to use the cancel button now

[NicerNewerCar]

@jcfr The cancel button does work as indented (I believe) it just won't allow you to interrupt mid-optimization (ie. you will have to wait for the current frame to finish optimizing before it will stop)