[E-devel] Fix issues with edge bindings

[Nick H. <me...@me...>]

So the edge bindings have once again ticked me off.  So much so that
I've made the attached patch to correct it's flaws.  I tried to keep
as much of the mechanisms the same even though I don't exactly like how
it's done right now.

Anyway, the patch fixes a couple of things.

First it will hide any of the edge windows if that edge is not being
used.  It is pointless to have the entire 1px border of the screen
unusable when I have no edge bindings.

Second it fixes the behavior of the fullscreen option.  Previously the
edges were set above all windows, even fullscreen.  The only difference
with the option set was that events would be ignored, but the edge
window was still in the way stealing events.  It is much better to
actually layer things properly so that when a fullscreen app is active,
the edge windows are layered below it and thus do not get in the way at
all and don't even have to ignore the events because they never happen.

Patch attached.  I would just commit it, but I know I was met with
resistance for some reason the last time I brought these issues up.