Make it possible for panels to go all the way to the edge of the
shell. This is particularly important for panels that scroll, such
as the new power panel. All other panels are changed to compensate
for the loss of external padding.
https://bugzilla.gnome.org/show_bug.cgi?id=691229
This makes loading faster, with less I/O, avoids unnecessary
code duplication (around 1k lines shaved), and ensures that
all the panels link and work appropriately.
By the same token, it will stop external panels from being
created, and loaded.
https://bugzilla.gnome.org/show_bug.cgi?id=690036
This prevents window resizes from making the first visit to the
mouse test area one that doesn't scroll all the way to the bottom.
1. Open System Settings
2. Open a panel that's smaller than the mouse one (eg. Background)
3. Back to overview
4. Open Mouse panel, click on test button
https://bugzilla.gnome.org/show_bug.cgi?id=684817
