Removing a TP from UI blocks UI again

[unho]

Removing a TP from UI now takes a long time, thus freezing the UI. I tested it only with a terminology project (relatively small in size) and it took more than 5 seconds. The blocking tasks should be moved to a background async process if possible to speed up the responsiveness.

[ta2-1]

There is no regression. We can’t do async job as when we add TP because all removing stuff should be called in one transaction. So the only thing I can think about is just to notify user that TP is marked for deletion and delete it async in one transaction. Though then we need to highlighted TP marked for deletion in UI somehow.