applets/taskmanager: disable window highlighting by default
Part of #149
This effect can trigger full-screen-flickering when invoked on maximized windows, which is distracting and disorienting. When there are multiple such windows and you make it happen by moving the pointer over their tasks, it can actually trigger a seizure in people sensitive to that kind of thing, since the flickering happens at faster than 3 Hz.
The effect is therefore too dangerous to have on by default; disable it.
Edited by Nate Graham