Add "highest window per monitor" option to intellihide

[nicka101]

This pull request adds a "Highest window per Monitor" option to intellihide, which replicates the behaviour of Dash-to-dock's intellihide, and only hides when obstructed by the top window on the monitor

[jderose9]

@charlesg99 Do you have any thoughts on this and #769 ? They both seem to be complete / working but they both seem to solve the primary use case described by @mtsoltan:

if the user had selected to hide bar in focused windows, the bottom part of the movie / video will be hidden (since it's not focused) - and if the user had selected to hide bar in maximized windows, part of the active window he's working on will be hidden under the bar since it's not maximized.

However, in the 769 implementation, in the context of a single monitor, when a non-fullscreen window is focused and away from the panel but has a full screen window behind it, the taskbar would be hidden, and in this one it would be visible. I'm not sure if that detail is really relevant or if we can pick one preferred behavior.

[charlesg99]

Hey guys! The problem is that the collision detection doesn't take into account the monitor the window is on. When implementing it, I first tried the "per monitor way" and had some problems as a window is always attached to a single monitor, but can span on more than one monitor and overlap more than one panel. As it is now, a single window being in this situation can hide more than one panel, which is what makes the most sense to me.

Having said that, currently this PR doesn't make much sense to me as "the highest window per monitor" could still be over more than one panel, but would only affect the one being on the same monitor as the highest window. I think it needs to be adjusted to check all panels proximity against all the highest windows. That way it would work and also fulfill #769's goal, in a more generic way.

We can leave this one open for now and adjust it later on. Thanks!