Xfce4 usability

Hi - I've been tweaking Numix's xfwm4 theme for greater usability (by my standards, anyway). Would you be interested in accepting:

* For those of us with single bottom panels or docks: when a window is maximized, allow the top-left and top-right pixels of the screen to hit window buttons that might be there.
* Bigger grips all round, because Xfwm4 doesn't have modern magic window borders that can be dragged even if the mouse isn't pointing at them, and 2 pixels is way too small for mice or (especially) tablets.
* Nice wide L-shaped bottom corner resize grips, rather than a measly 2x2 pixel blob.
* Optionally (separate commit), bigger grips only on the bottom ☺
* Bigger titlebar buttons, to make clicking them easier (and possible on the top row of screen pixels when the window is maximized). Note the glyph size and the spaces between them remains unchanged.
* Icons can be rebuilt from SVG, to ease maintenance. Slight stylistic change as a result, but still pretty much a pixel-perfect match to upstream ☺
* Add stick button. Xfwm now has its full complement of button types.