Module selection on right-click behaves inconsistently.

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Start DeVIDE
2. Add one or more modules to the canvas
3. Right click a module without selecting it first

What is the expected output? What do you see instead?
It seems the selection is only partially set to the object: the top part of 
the menu reflects the clicked module, while the bottom part is disabled or 
reflects a previous selection. This can be seen with the following steps:
1. Add two different modules
2. Select module 1
3. Right click module 2, select Block Selected
Module 1 is blocked rather than module 2. Expected result is that module 2 
would be selected and blocked.

Right-click behavior should be changed to the following to be consistent 
with most applications:
* Right-clicking any object when it is selected (or part of a larger 
selection) just opens the context menu.
* Right clicking an unselected object will replace the current selection by 
the object which was clicked, and then open the context menu for the 
clicked object.
* To help with selections of more than one module, right clicking an empty 
area should not clear the selection (this works in current revisions).
* Selected objects should be highlighted before (while) the context menu is 
shown.

Original issue reported on code.google.com by [email protected] on 18 Sep 2008 at 2:30