Editable modifications

Here, as requested, my modifications of supercamel code.
Here a list of changes from supercamel's code:
- disable check for modifier keys when a mouse click is received
- remove a drawing statement before the drawing pointer (or whatever cairo calls it) is is place
-change signal name from `changed` to `point-changed` (the reason is simple, it looks more informative to me)
-replace the 4.0 dot radius with a macro called DOT_RADIUS (also make the click recognition depend on this)
-fix white-spaces