DiaCanvas2 behavior

DiaCanvas has some pre-implemented behavior. I think it should be the
same over all applications that use DiaCanvas...

Mouse:
~~~~~
The mouse can move freely over the canvas. it can select objects by clicking
on them (button_press) and unselect objects by clicking next to the object or
on another object. When holding the SHIFT key no objects are unselected when
you click, when holding CONTROL (CTRL) the selection is switched: if
the object is not selected, it becomes selected, if the object is selected it
becomes unselected (and does not recieve the event).

When you press the button in the free sector (not on an object) and drag the
mouse, a selectin box will appear. When you release the selection box all
objects that are inside the selection box (as a whole or for a part) will
become selected. When SHIFT or CONTROL is held no objects are unselected.

Keyboard:
~~~~~~~~
Keyboard bindings will be GIMP like:
'-'	zoom out
'='	zoom in
'1'	set zoom to 100%
'C-C'	copy selected objects
'C-X'	cut selected objects
'C-V'	paste selected objects
'Del'	Remove selected objects from the canvas
'C-Z'	undo last change
'C-R'	redo last undo action

Arjan
