window: allow moving maximized surface

Moving maximized surface will cause compositor to unsnap it
window-manager: pass correct flag to theme_get_location

We need to pass THEME_FRAME_MAXIMIZED to theme_get_location to detect
correct cursor position
xwm: Add and hook up min/max/close titlebar buttons
theme: Change to a darker more neutral theme
wds: Remove padding for clock position
Change bug reporting link

We don't want to cause confusion by having users reporting bugs for these patches to the upstream official tracker for potential bugs in this code. Change the link to reflect the proper tracker.
shell: unsnap window when moving it in maximized state

This patch allows moving maximized surface through compositor binding.
When maximized surface is moved, its restored to its original size and
grab point is on middle upper part of the surface.
Merge branch 'maximize_fix_3' of https://github.com/rafalmiel/weston into next

Conflicts:
	src/shell.c
	src/xwayland/window-manager.c
shell: Fix crash when a surface is destroyed during a grab

If a client crashes, the shell_surface(s) will be destroyed. If
a grab was present, we now destroy the grab when destroying the
surface.
toytoolkit: Fix crash when a surface is destroyed during a grab

The desktop shell client might crash if a the focus_surface pointer
is set to NULL while a grab is being held. Because this pointer variable
is not always valid, here we always check that it is not NULL before
using it.