Support negative positions referring to the right and bottom edges

[mfvianna]

X11's --geometry also supported positions like -300-200 to position a window 300 pixels to the left of the right screen edge and 200 pixels above of the bottom screen edge.

kdotool could also accept negative values for the windomove command likewise:
kdotool windowmove -300 -100

actually a new setwinidowgeometry command sharing the --geometry syntax would be very handy. Some examples:
500x300-100-100
+300-100
400x200
1024x768+50-100

To run the extra mile, some completely new aliases for the windowmove command would also be very handy:
center (center of the screen)
top (screen top, centered vertically)
bottom (screen bottom, centered vertically)
left (screen left, centered horizontally)
right (screen right, centered horizontally)

...as well as for the corners:
topleft
topright
bottomleft
bottomright